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how do you draw a single bond in a lewis structure?

Affiliate seven. Chemical Bonding and Molecular Geometry

vii.three Lewis Symbols and Structures

Learning Objectives

By the end of this section, yous will be able to:

  • Write Lewis symbols for neutral atoms and ions
  • Depict Lewis structures depicting the bonding in uncomplicated molecules

Thus far in this chapter, nosotros have discussed the various types of bonds that form between atoms and/or ions. In all cases, these bonds involve the sharing or transfer of valence vanquish electrons between atoms. In this section, nosotros volition explore the typical method for depicting valence shell electrons and chemical bonds, namely Lewis symbols and Lewis structures.

Lewis Symbols

Nosotros utilize Lewis symbols to draw valence electron configurations of atoms and monatomic ions. A Lewis symbol consists of an elemental symbol surrounded by 1 dot for each of its valence electrons:

A Lewis structure of calcium is shown. A lone pair of electrons are shown to the right of the symbol.

Effigy 1 shows the Lewis symbols for the elements of the third period of the periodic table.

A table is shown that has three columns and nine rows. The header row reads
Figure i. Lewis symbols illustrating the number of valence electrons for each chemical element in the 3rd period of the periodic table.

Lewis symbols can likewise be used to illustrate the germination of cations from atoms, as shown here for sodium and calcium:

Two diagrams are shown. The left diagram shows a Lewis dot structure of sodium with one dot, then a right-facing arrow leading to a sodium symbol with a superscripted plus sign, a plus sign, and the letter

As well, they can exist used to evidence the germination of anions from atoms, as shown here for chlorine and sulfur:

Two diagrams are shown. The left diagram shows a Lewis dot structure of chlorine with seven dots and the letter

Figure 2 demonstrates the use of Lewis symbols to evidence the transfer of electrons during the formation of ionic compounds.

A table is shown with four rows. The header row reads
Figure 2. Cations are formed when atoms lose electrons, represented by fewer Lewis dots, whereas anions are formed past atoms gaining electrons. The full number of electrons does non change.

Lewis Structures

We also apply Lewis symbols to betoken the formation of covalent bonds, which are shown in Lewis structures, drawings that describe the bonding in molecules and polyatomic ions. For example, when two chlorine atoms form a chlorine molecule, they share one pair of electrons:

A Lewis dot diagram shows a reaction. Two chlorine symbols, each surrounded by seven dots are separated by a plus sign. The dots on the first atom are all black and the dots on the second atom are all read. The phrase,

The Lewis structure indicates that each Cl atom has 3 pairs of electrons that are not used in bonding (chosen lone pairs) and one shared pair of electrons (written between the atoms). A dash (or line) is sometimes used to indicate a shared pair of electrons:

Two Lewis structures are shown. The left-hand structure shows two H atoms connected by a single bond. The right-hand structure shows two C l atoms connected by a single bond and each surrounded by six dots.

A unmarried shared pair of electrons is chosen a single bail. Each Cl atom interacts with eight valence electrons: the half-dozen in the lone pairs and the two in the single bond.

The Octet Dominion

The other halogen molecules (Fii, Br2, I2, and Attwo) class bonds similar those in the chlorine molecule: 1 single bond between atoms and 3 alone pairs of electrons per atom. This allows each halogen atom to have a element of group 0 electron configuration. The tendency of primary grouping atoms to form enough bonds to obtain eight valence electrons is known as the octet rule.

The number of bonds that an cantlet can form can often be predicted from the number of electrons needed to reach an octet (8 valence electrons); this is peculiarly true of the nonmetals of the second period of the periodic table (C, N, O, and F). For example, each atom of a group 14 chemical element has four electrons in its outermost shell and therefore requires 4 more than electrons to achieve an octet. These four electrons tin can be gained by forming four covalent bonds, every bit illustrated here for carbon in CCl4 (carbon tetrachloride) and silicon in SiHiv (silane). Considering hydrogen simply needs two electrons to fill its valence vanquish, information technology is an exception to the octet rule. The transition elements and inner transition elements as well do not follow the octet rule:

Two sets of Lewis dot structures are shown. The left structures depict five C l symbols in a cross shape with eight dots around each, the word

Grouping 15 elements such every bit nitrogen have five valence electrons in the diminutive Lewis symbol: one lone pair and three unpaired electrons. To obtain an octet, these atoms class 3 covalent bonds, equally in NH3 (ammonia). Oxygen and other atoms in group xvi obtain an octet past forming 2 covalent bonds:

Three Lewis structures labeled,

Double and Triple Bonds

As previously mentioned, when a pair of atoms shares i pair of electrons, nosotros phone call this a unmarried bond. Still, a pair of atoms may need to share more than one pair of electrons in society to attain the requisite octet. A double bond forms when two pairs of electrons are shared betwixt a pair of atoms, equally between the carbon and oxygen atoms in CH2O (formaldehyde) and between the two carbon atoms in C2H4 (ethylene):

Two pairs of Lewis structures are shown. The left pair of structures shows a carbon atom forming single bonds to two hydrogen atoms. There are four electrons between the C atom and an O atom. The O atom also has two pairs of dots. The word

A triple bond forms when three electron pairs are shared by a pair of atoms, as in carbon monoxide (CO) and the cyanide ion (CN):

Two pairs of Lewis structures are shown and connected by a right-facing arrow. The left pair of structures show a C atom and an O atom with six dots in between them and a lone pair on each. The word

Writing Lewis Structures with the Octet Rule

For very simple molecules and molecular ions, we tin write the Lewis structures by merely pairing up the unpaired electrons on the elective atoms. Come across these examples:

Three reactions are shown with Lewis dot diagrams. The first shows a hydrogen with one red dot, a plus sign and a bromine with seven dots, one of which is red, connected by a right-facing arrow to a hydrogen and bromine with a pair of red dots in between them. There are also three lone pairs on the bromine. The second reaction shows a hydrogen with a coefficient of two and one red dot, a plus sign, and a sulfur atom with six dots, two of which are red, connected by a right facing arrow to two hydrogen atoms and one sulfur atom. There are two red dots in between the two hydrogen atoms and the sulfur atom. Both pairs of these dots are red. The sulfur atom also has two lone pairs of dots. The third reaction shows two nitrogen atoms each with five dots, three of which are red, separated by a plus sign, and connected by a right-facing arrow to two nitrogen atoms with six red electron dots in between one another. Each nitrogen atom also has one lone pair of electrons.

For more complicated molecules and molecular ions, information technology is helpful to follow the pace-by-step procedure outlined here:

  1. Determine the total number of valence (outer beat) electrons. For cations, subtract ane electron for each positive charge. For anions, add together one electron for each negative charge.
  2. Depict a skeleton structure of the molecule or ion, arranging the atoms around a central atom. (Generally, the least electronegative element should be placed in the center.) Connect each cantlet to the primal cantlet with a single bond (i electron pair).
  3. Distribute the remaining electrons equally solitary pairs on the terminal atoms (except hydrogen), completing an octet around each cantlet.
  4. Place all remaining electrons on the primal atom.
  5. Rearrange the electrons of the outer atoms to brand multiple bonds with the central cantlet in order to obtain octets wherever possible.

Permit us decide the Lewis structures of SiH4, CHO2−, NO+, and OF2 as examples in following this procedure:

  1. Determine the total number of valence (outer shell) electrons in the molecule or ion.
    • For a molecule, we add the number of valence electrons on each atom in the molecule:

      [latex]\begin{assortment}{r r l} \text{SiH}_4 & & \\[1em] & \text{Si: iv valence electrons/atom} \times 1 \;\text{atom} & = 4 \\[1em] \dominion[-0.5ex]{21em}{0.1ex}\hspace{-21em} + & \text{H: ane valence electron/atom} \times 4 \;\text{atoms} & = 4 \\[1em] & & = 8 \;\text{valence electrons} \end{array}[/latex]

    • For a negative ion, such as CHO2 , we add the number of valence electrons on the atoms to the number of negative charges on the ion (one electron is gained for each unmarried negative charge):

      [latex]\begin{array}{r r l} {\text{CHO}_2}^{-} & & \\[1em] & \text{C: 4 valence electrons/atom} \times 1 \;\text{atom} & = 4 \\[1em] & \text{H: 1 valence electron/atom} \times ane \;\text{atom} & = 1 \\[1em] & \text{O: 6 valence electrons/atom} \times 2 \;\text{atoms} & = 12 \\[1em] \rule[-0.5ex]{21.5em}{0.1ex}\hspace{-21.5em} + & 1\;\text{additional electron} & = ane \\[1em] & & = xviii \;\text{valence electrons} \end{array}[/latex]

    • For a positive ion, such as NO+, we add the number of valence electrons on the atoms in the ion and and so decrease the number of positive charges on the ion (one electron is lost for each unmarried positive accuse) from the full number of valence electrons:

      [latex]\begin{array}{r r l} \text{NO}^{+} & & \\[1em] & \text{Northward: 5 valence electrons/atom} \times one \;\text{atom} & = v \\[1em] & \text{O: half-dozen valence electrons/atom} \times 1 \;\text{cantlet} & = half dozen \\[1em] \rule[-0.5ex]{21em}{0.1ex}\hspace{-21em} + & -1 \;\text{electron (positive accuse)} & = -one \\[1em] & & = 10 \;\text{valence electrons} \cease{array}[/latex]

    • Since OF2 is a neutral molecule, we simply add the number of valence electrons:

      [latex]\begin{array}{r r l} \text{OF}_{2} & & \\[1em] & \text{O: 6 valence electrons/cantlet} \times i \;\text{atom} & = 6 \\[1em] \dominion[-0.5ex]{21em}{0.1ex}\hspace{-21em} + & \text{F: 7 valence electrons/atom} \times 2 \;\text{atoms} & = xiv \\[1em] & & = 20 \;\text{valence electrons} \end{array}[/latex]

  2. Draw a skeleton structure of the molecule or ion, arranging the atoms effectually a fundamental atom and connecting each atom to the cardinal cantlet with a unmarried (one electron pair) bail. (Notation that we denote ions with brackets around the structure, indicating the charge exterior the brackets:)Four Lewis diagrams are shown. The first shows one silicon single boned to four hydrogen atoms. The second shows a carbon which forms a single bond with an oxygen and a hydrogen and a double bond with a second oxygen. This structure is surrounded by brackets and has a superscripted negative sign near the upper right corner. The third structure shows a nitrogen single bonded to an oxygen and surrounded by brackets with a superscripted plus sign in the upper right corner. The last structure shows two fluorine atoms single bonded to a central oxygen.When several arrangements of atoms are possible, every bit for CHOtwo , we must employ experimental evidence to choose the correct ane. In general, the less electronegative elements are more likely to be primal atoms. In CHO2 , the less electronegative carbon atom occupies the central position with the oxygen and hydrogen atoms surrounding it. Other examples include P in POCl3, S in And so2, and Cl in ClO4 . An exception is that hydrogen is almost never a central cantlet. As the nigh electronegative element, fluorine also cannot be a central atom.
  3. Distribute the remaining electrons every bit lone pairs on the concluding atoms (except hydrogen) to complete their valence shells with an octet of electrons.
    • There are no remaining electrons on SiHiv, then it is unchanged:Four Lewis structures are shown. The first shows one silicon single boned to four hydrogen atoms. The second shows a carbon single bonded to two oxygen atoms that each have three lone pairs and single bonded to a hydrogen. This structure is surrounded by brackets and has a superscripted negative sign near the upper right corner. The third structure shows a nitrogen single bonded to an oxygen, each with three lone pairs of electrons. This structure is surrounded by brackets with a superscripted plus sign in the upper right corner. The last structure shows two fluorine atoms, each with three lone pairs of electrons, single bonded to a central oxygen.
  4. Place all remaining electrons on the cardinal atom.
    • For SiHiv, CHO2 , and NO+, there are no remaining electrons; we already placed all of the electrons determined in Step 1.
    • For OFtwo, we had sixteen electrons remaining in Pace 3, and we placed 12, leaving 4 to exist placed on the central atom:A Lewis structure shows two fluorine atoms, each with three lone pairs of electrons, single bonded to a central oxygen which has two lone pairs of electrons.
  5. Rearrange the electrons of the outer atoms to brand multiple bonds with the central cantlet in guild to obtain octets wherever possible.

Example i

Writing Lewis Structures
NASA'southward Cassini-Huygens mission detected a large cloud of toxic hydrogen cyanide (HCN) on Titan, one of Saturn'southward moons. Titan also contains ethane (HthreeCCH3), acetylene (HCCH), and ammonia (NH3). What are the Lewis structures of these molecules?

Solution

  1. Summate the number of valence electrons.HCN: (1 × 1) + (four × 1) + (v × one) = 10H3CCHthree: (1 × 3) + (ii × 4) + (1 × iii) = 14HCCH: (ane × i) + (ii × 4) + (1 × 1) = 10NHthree: (5 × 1) + (3 × 1) = 8
  2. Draw a skeleton and connect the atoms with single bonds. Remember that H is never a central atom:Four Lewis structures are shown. The first structure shows a carbon atom single bonded to a hydrogen atom and a nitrogen atom. The second structure shows two carbon atoms single bonded to one another. Each is single bonded to three hydrogen atoms. The third structure shows two carbon atoms single bonded to one another and each single bonded to one hydrogen atom. The fourth structure shows a nitrogen atom single bonded to three hydrogen atoms.
  3. Where needed, distribute electrons to the terminal atoms: Four Lewis structures are shown. The first structure shows a carbon atom single bonded to a hydrogen atom and a nitrogen atom, which has three lone pairs of electrons. The second structure shows two carbon atoms single bonded to one another. Each is single bonded to three hydrogen atoms. The third structure shows two carbon atoms single bonded to one another and each single bonded to one hydrogen atom. The fourth structure shows a nitrogen atom single bonded to three hydrogen atoms.HCN: half-dozen electrons placed on NH3CCH3: no electrons remainHCCH: no final atoms capable of accepting electrons

    NH3: no terminal atoms capable of accepting electrons

  4. Where needed, place remaining electrons on the key atom: Four Lewis structures are shown. The first structure shows a carbon atom single bonded to a hydrogen atom and a nitrogen atom, which has three lone pairs of electrons. The second structure shows two carbon atoms single bonded to one another. Each is single bonded to three hydrogen atoms. The third structure shows two carbon atoms, each with a lone pair of electrons, single bonded to one another and each single bonded to one hydrogen atom. The fourth structure shows a nitrogen atom with a lone pair of electrons single bonded to three hydrogen atoms.HCN: no electrons remainH3CCHthree: no electrons remainHCCH: four electrons placed on carbon

    NH3: ii electrons placed on nitrogen

  5. Where needed, rearrange electrons to class multiple bonds in lodge to obtain an octet on each cantlet:HCN: grade two more C–N bondsH3CCH3: all atoms have the correct number of electronsHCCH: form a triple bond between the two carbon atomsNH3: all atoms have the correct number of electrons

    Four Lewis structures are shown. The first structure shows a carbon atom single bonded to a hydrogen atom and a nitrogen atom, which has three lone pairs of electrons. Two curved arrows point from the nitrogen to the carbon. Below this structure is the word

Cheque Your Learning
Both carbon monoxide, CO, and carbon dioxide, CO2, are products of the combustion of fossil fuels. Both of these gases also cause problems: CO is toxic and COtwo has been implicated in global climatic change. What are the Lewis structures of these 2 molecules?

Answer:

Two Lewis structures are shown. The left shows a carbon triple bonded to an oxygen, each with a lone electron pair. The right structure shows a carbon double bonded to an oxygen on each side. Each oxygen has two lone pairs of electrons.

Fullerene Chemistry

Carbon soot has been known to man since prehistoric times, just it was non until fairly recently that the molecular structure of the main component of soot was discovered. In 1996, the Nobel Prize in Chemistry was awarded to Richard Smalley (Figure 3), Robert Curl, and Harold Kroto for their work in discovering a new form of carbon, the C60 buckminsterfullerene molecule (Figure 1 in Affiliate 7 Introduction). An entire class of compounds, including spheres and tubes of various shapes, were discovered based on C60. This type of molecule, called a fullerene, shows promise in a variety of applications. Because of their size and shape, fullerenes can encapsulate other molecules, then they accept shown potential in various applications from hydrogen storage to targeted drug delivery systems. They likewise possess unique electronic and optical properties that accept been put to good apply in solar powered devices and chemic sensors.

A photo of Richard Smalley is shown.
Figure 3. Richard Smalley (1943–2005), a professor of physics, chemical science, and astronomy at Rice Academy, was one of the leading advocates for fullerene chemical science. Upon his death in 2005, the United states Senate honored him as the "Father of Nanotechnology." (credit: United States Department of Free energy)

Exceptions to the Octet Rule

Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules autumn into three categories:

  • Odd-electron molecules have an odd number of valence electrons, and therefore accept an unpaired electron.
  • Electron-deficient molecules have a central atom that has fewer electrons than needed for a noble gas configuration.
  • Hypervalent molecules have a cardinal atom that has more electrons than needed for a noble gas configuration.

Odd-electron Molecules

We phone call molecules that comprise an odd number of electrons gratuitous radicals. Nitric oxide, NO, is an example of an odd-electron molecule; it is produced in internal combustion engines when oxygen and nitrogen react at loftier temperatures.

To depict the Lewis structure for an odd-electron molecule like NO, we follow the same five steps we would for other molecules, but with a few minor changes:

  1. Determine the total number of valence (outer shell) electrons. The sum of the valence electrons is 5 (from North) + 6 (from O) = 11. The odd number immediately tells the states that nosotros take a free radical, and then nosotros know that not every atom tin accept eight electrons in its valence shell.
  2. Draw a skeleton structure of the molecule. We can easily draw a skeleton with an Northward–O unmarried bond:Northward–O
  3. Distribute the remaining electrons equally solitary pairs on the concluding atoms. In this case, there is no central atom, and then we distribute the electrons effectually both atoms. Nosotros give eight electrons to the more electronegative atom in these situations; thus oxygen has the filled valence crush:
    A Lewis structure shows a nitrogen atom, with one lone pair and one lone electron single bonded to an oxygen atom with three lone pairs of electrons.
  4. Place all remaining electrons on the central atom. Since there are no remaining electrons, this step does not employ.
  5. Rearrange the electrons to brand multiple bonds with the fundamental atom in order to obtain octets wherever possible. We know that an odd-electron molecule cannot take an octet for every cantlet, but we desire to get each atom as shut to an octet as possible. In this case, nitrogen has but 5 electrons around it. To move closer to an octet for nitrogen, we accept one of the lone pairs from oxygen and use information technology to form a NO double bond. (We cannot take another alone pair of electrons on oxygen and grade a triple bond because nitrogen would and so have ix electrons:)
    A Lewis structure shows a nitrogen atom, with one lone pair and one lone electron double bonded to an oxygen atom with two lone pairs of electrons.

Electron-scarce Molecules

Nosotros will also encounter a few molecules that contain central atoms that practise not have a filled valence shell. Generally, these are molecules with central atoms from groups 2 and 12, outer atoms that are hydrogen, or other atoms that practice not class multiple bonds. For example, in the Lewis structures of beryllium dihydride, BeH2, and boron trifluoride, BFthree, the beryllium and boron atoms each have only four and half dozen electrons, respectively. It is possible to draw a structure with a double bond between a boron atom and a fluorine atom in BF3, satisfying the octet rule, just experimental evidence indicates the bond lengths are closer to that expected for B–F single bonds. This suggests the best Lewis structure has 3 B–F single bonds and an electron deficient boron. The reactivity of the compound is also consistent with an electron deficient boron. Nevertheless, the B–F bonds are slightly shorter than what is actually expected for B–F single bonds, indicating that some double bond character is constitute in the actual molecule.

Two Lewis structures are shown. The left shows a beryllium atom single bonded to two hydrogen atoms. The right shows a boron atom single bonded to three fluorine atoms, each with three lone pairs of electrons.

An atom like the boron atom in BF3, which does not accept eight electrons, is very reactive. Information technology readily combines with a molecule containing an atom with a lone pair of electrons. For instance, NHthree reacts with BFthree because the lone pair on nitrogen can be shared with the boron atom:

A reaction is shown with three Lewis diagrams. The left diagram shows a boron atom single bonded to three fluorine atoms, each with three lone pairs of electrons. There is a plus sign. The next structure shows a nitrogen atom with one lone pair of electrons single bonded to three hydrogen atoms. A right-facing arrow leads to the final Lewis structure that shows a boron atom single bonded to a nitrogen atom and single bonded to three fluorine atoms, each with three lone pairs of electrons. The nitrogen atom is also single bonded to three hydrogen atoms. The bond between the boron atom and the nitrogen atom is colored red.

Hypervalent Molecules

Elements in the second period of the periodic table (northward = 2) can accommodate only eight electrons in their valence crush orbitals because they have only four valence orbitals (one 2s and three 2p orbitals). Elements in the 3rd and higher periods (n ≥ three) have more than four valence orbitals and tin can share more than than 4 pairs of electrons with other atoms considering they have empty d orbitals in the same shell. Molecules formed from these elements are sometimes called hypervalent molecules. Effigy 4 shows the Lewis structures for 2 hypervalent molecules, PClv and SFvi.

Two Lewis structures are shown. The left shows a phosphorus atom single bonded to five chlorine atoms, each with three lone pairs of electrons. The right shows a sulfur atom single bonded to six fluorine atoms, each with three lone pairs of electrons.
Figure 4. In PCl5, the central atom phosphorus shares five pairs of electrons. In SFhalf-dozen, sulfur shares vi pairs of electrons.

In some hypervalent molecules, such as IF5 and XeF4, some of the electrons in the outer shell of the central cantlet are lone pairs:

Two Lewis structures are shown. The left shows an iodine atom with one lone pair single bonded to five fluorine atoms, each with three lone pairs of electrons. The right diagram shows a xenon atom with two lone pairs of electrons single bonded to four fluorine atoms, each with three lone pairs of electrons.

When we write the Lewis structures for these molecules, we discover that we have electrons left over later filling the valence shells of the outer atoms with eight electrons. These additional electrons must be assigned to the fundamental atom.

Example two

Writing Lewis Structures: Octet Rule Violations
Xenon is a noble gas, only it forms a number of stable compounds. Nosotros examined XeF4 before. What are the Lewis structures of XeF2 and XeF6?

Solution
We can draw the Lewis structure of any covalent molecule by following the six steps discussed earlier. In this case, we can condense the final few steps, since not all of them employ.

  1. Calculate the number of valence electrons: XeF2: 8 + (2 × 7) = 22XeF6: 8 + (6 × 7) = 50
  2. Draw a skeleton joining the atoms by single bonds. Xenon will exist the central cantlet because fluorine cannot be a central atom:
    Two Lewis diagrams are shown. The left depicts a xenon atom single bonded to two fluorine atoms. The right shows a xenon atom single bonded to six fluorine atoms.
  3. Distribute the remaining electrons.XeF2: We identify three lone pairs of electrons around each F atom, accounting for 12 electrons and giving each F atom 8 electrons. Thus, six electrons (three alone pairs) remain. These lone pairs must exist placed on the Xe atom. This is acceptable because Xe atoms have empty valence shell d orbitals and tin can accommodate more than eight electrons. The Lewis structure of XeFtwo shows two bonding pairs and 3 lone pairs of electrons effectually the Xe atom:
    A Lewis diagram shows a xenon atom with three lone pairs of electrons single bonded to two fluorine atoms, each with three lone pairs of electrons.XeF6: We place three lone pairs of electrons around each F atom, bookkeeping for 36 electrons. Two electrons remain, and this lone pair is placed on the Xe atom:This structure shows a xenon atom single bonded to six fluorine atoms. Each fluorine atom has three lone pairs of electrons.

Check Your Learning
The halogens form a class of compounds chosen the interhalogens, in which halogen atoms covalently bond to each other. Write the Lewis structures for the interhalogens BrCl3 and IClfour .

Answer:

Two Lewis structures are shown. The left depicts a bromine atom with two lone pairs of electrons single bonded to three chlorine atoms, each with three lone pairs of electrons. The right shows an iodine atom, with two lone pairs of electrons, single boned to four chlorine atoms, each with three lone pairs of electrons. This structure is surrounded by brackets and has a superscripted negative sign.

Key Concepts and Summary

Valence electronic structures can exist visualized past drawing Lewis symbols (for atoms and monatomic ions) and Lewis structures (for molecules and polyatomic ions). Lone pairs, unpaired electrons, and single, double, or triple bonds are used to indicate where the valence electrons are located around each cantlet in a Lewis structure. Almost structures—especially those containing 2nd row elements—obey the octet rule, in which every atom (except H) is surrounded by eight electrons. Exceptions to the octet rule occur for odd-electron molecules (gratuitous radicals), electron-deficient molecules, and hypervalent molecules.

Chemistry End of Chapter Exercises

  1. Write the Lewis symbols for each of the following ions:

    (a) As3–

    (b) I

    (c) Beii+

    (d) Oii–

    (e) Ga3+

    (f) Li+

    (yard) Nthree–

  2. Many monatomic ions are constitute in seawater, including the ions formed from the post-obit list of elements. Write the Lewis symbols for the monatomic ions formed from the following elements:

    (a) Cl

    (b) Na

    (c) Mg

    (d) Ca

    (e) Grand

    (f) Br

    (g) Sr

    (h) F

  3. Write the Lewis symbols of the ions in each of the post-obit ionic compounds and the Lewis symbols of the atom from which they are formed:

    (a) MgS

    (b) Al2O3

    (c) GaCliii

    (d) KtwoO

    (eastward) LithreeNorthward

    (f) KF

  4. In the Lewis structures listed hither, Grand and Ten correspond various elements in the third period of the periodic table. Write the formula of each compound using the chemical symbols of each element:

    (a)

    Two Lewis structures are shown side-by-side, each surrounded by brackets. The left structure shows the symbol M with a superscripted two positive sign. The right shows the symbol X surrounded by four lone pairs of electrons with a superscripted two negative sign outside of the brackets.

    (b)

    Two Lewis structures are shown side-by-side, each surrounded by brackets. The left structure shows the symbol M with a superscripted three positive sign. The right structure shows the symbol X surrounded by four lone pairs of electrons with a superscripted negative sign and a subscripted three both outside of the brackets.

    (c)

    Two Lewis structures are shown side-by-side, each surrounded by brackets. The left structure shows the symbol M with a superscripted positive sign and a subscripted two outside of the brackets. The right structure shows the symbol X surrounded by four lone pairs of electrons with a superscripted two negative sign outside of the brackets.

    (d)

    Two Lewis structures are shown side-by-side, each surrounded by brackets. The left structure shows the symbol M with a superscripted three positive sign and a subscripted two outside of the brackets. The right structure shows the symbol X surrounded by four lone pairs of electrons with a superscripted two negative sign and subscripted three both outside of the brackets.

  5. Write the Lewis structure for the diatomic molecule P2, an unstable grade of phosphorus found in loftier-temperature phosphorus vapor.
  6. Write Lewis structures for the post-obit:

    (a) H2

    (b) HBr

    (c) PCl3

    (d) SFii

    (east) H2CCH2

    (f) HNNH

    (one thousand) HiiCNH

    (h) NO

    (i) Nii

    (j) CO

    (thousand) CN

  7. Write Lewis structures for the following:

    (a) O2

    (b) HiiCO

    (c) AsFiii

    (d) ClNO

    (e) SiCliv

    (f) H3O+

    (g) NH4 +

    (h) BF4

    (i) HCCH

    (j) ClCN

    (k) C2 2+

  8. Write Lewis structures for the following:

    (a) ClFiii

    (b) PCl5

    (c) BFthree

    (d) PF6

  9. Write Lewis structures for the following:

    (a) SeF6

    (b) XeF4

    (c) SeCl3 +

    (d) Cl2BBCltwo (contains a B–B bail)

  10. Write Lewis structures for:

    (a) POfour three−

    (b) ICl4

    (c) Then3 2−

    (d) HONO

  11. Correct the post-obit argument: "The bonds in solid PbClii are ionic; the bond in a HCl molecule is covalent. Thus, all of the valence electrons in PbCltwo are located on the Cl ions, and all of the valence electrons in a HCl molecule are shared between the H and Cl atoms."
  12. Write Lewis structures for the following molecules or ions:

    (a) SbHiii

    (b) XeF2

    (c) Se8 (a cyclic molecule with a ring of eight Se atoms)

  13. Methanol, H3COH, is used as the fuel in some race cars. Ethanol, C2H5OH, is used extensively every bit motor fuel in Brazil. Both methanol and ethanol produce CO2 and H2O when they burn. Write the chemical equations for these combustion reactions using Lewis structures instead of chemical formulas.
  14. Many planets in our solar arrangement contain organic chemicals including methane (CH4) and traces of ethylene (C2H4), ethane (C2H6), propyne (H3CCCH), and diacetylene (HCCCCH). Write the Lewis structures for each of these molecules.
  15. Carbon tetrachloride was formerly used in fire extinguishers for electrical fires. It is no longer used for this purpose because of the formation of the toxic gas phosgene, CliiCO. Write the Lewis structures for carbon tetrachloride and phosgene.
  16. Identify the atoms that correspond to each of the following electron configurations. So, write the Lewis symbol for the common ion formed from each cantlet:

    (a) 1south 2iisouthward 22p 5

    (b) anes two2south 22p 63s 2

    (c) 1s 22south twotwop six3s 2iiip viivs ii3d 10

    (d) 1s 22s 22p half dozenthrees 23p half dozenivs 23d 10ivp iv

    (e) 1southward 22s iiiip half dozen3south 23p 64s two3d 104p 1

  17. The arrangement of atoms in several biologically important molecules is given here. Consummate the Lewis structures of these molecules by adding multiple bonds and lone pairs. Practice non add any more atoms.

    (a) the amino acid serine:

    A Lewis structure is shown. A nitrogen atom is single bonded to two hydrogen atoms and a carbon atom. The carbon atom is single bonded to a hydrogen atom and two other carbon atoms. One of these carbon atoms is single bonded to two hydrogen atoms and an oxygen atom. The oxygen atom is bonded to a hydrogen atom. The other carbon atom is single bonded to two oxygen atoms, one of which is bonded to a hydrogen atom.

    (b) urea:

    A Lewis structure is shown. A nitrogen atom is single bonded to two hydrogen atoms and a carbon atom. The carbon atom is single bonded to an oxygen atom and another nitrogen atom. That nitrogen atom is then single bonded to two hydrogen atoms.

    (c) pyruvic acrid:

    A Lewis structure is shown. A carbon atom is single bonded to three hydrogen atoms and another carbon atom. The second carbon atom is single bonded to an oxygen atom and a third carbon atom. This carbon is then single bonded to two oxygen atoms, one of which is single bonded to a hydrogen atom.

    (d) uracil:

    A Lewis hexagonal ring structure is shown. From the top of the ring (moving clockwise), three carbon atoms, one nitrogen atom, a carbon atom, and a nitrogen atom are single bonded to each another. The top carbon atom is single bonded to an oxygen atom. The second and third carbons and the nitrogen atom are each single bonded to a hydrogen atom. The next carbon atom is single bonded to an oxygen atom, and the last nitrogen atom is single bonded to a hydrogen atom.

    (e) carbonic acrid:

    A Lewis structure is shown. A carbon atom is single bonded to three oxygen atoms. Two of those oxygen atoms are each single bonded to a hydrogen atom.

  18. A compound with a molar mass of about 28 g/mol contains 85.seven% carbon and 14.three% hydrogen by mass. Write the Lewis structure for a molecule of the compound.
  19. A chemical compound with a molar mass of about 42 g/mol contains 85.seven% carbon and 14.iii% hydrogen by mass. Write the Lewis structure for a molecule of the compound.
  20. Two arrangements of atoms are possible for a chemical compound with a tooth mass of about 45 thousand/mol that contains 52.two% C, 13.i% H, and 34.7% O by mass. Write the Lewis structures for the ii molecules.
  21. How are single, double, and triple bonds similar? How practice they differ?

Glossary

double bond
covalent bail in which ii pairs of electrons are shared between two atoms
free radical
molecule that contains an odd number of electrons
hypervalent molecule
molecule containing at least one principal group chemical element that has more eight electrons in its valence shell
Lewis structure
diagram showing lone pairs and bonding pairs of electrons in a molecule or an ion
Lewis symbol
symbol for an chemical element or monatomic ion that uses a dot to stand for each valence electron in the chemical element or ion
lone pair
2 (a pair of) valence electrons that are not used to form a covalent bond
octet rule
guideline that states main group atoms will course structures in which eight valence electrons interact with each nucleus, counting bonding electrons as interacting with both atoms connected by the bond
unmarried bail
bond in which a unmarried pair of electrons is shared between 2 atoms
triple bail
bail in which three pairs of electrons are shared between two atoms

Solutions

Answers to Chemistry End of Chapter Exercises

ane. (a) viii electrons:
A Lewis dot diagram shows the symbol for arsenic, A s, surrounded by eight dots and a superscripted three negative sign.;

(b) eight electrons:

A Lewis dot diagram shows the symbol for iodine, I, surrounded by eight dots and a superscripted negative sign.;

(c) no electrons

Exist2+;

(d) 8 electrons:

A Lewis dot diagram shows the symbol for oxygen, O, surrounded by eight dots and a superscripted two negative sign.;

(e) no electrons

Ga3+;

(f) no electrons

Li+;

(g) eight electrons:

A Lewis dot diagram shows the symbol for nitrogen, N, surrounded by eight dots and a superscripted three negative sign.

3. (a)

Two Lewis structures are shown. The left shows the symbol M g with a superscripted two positive sign while the right shows the symbol S surrounded by eight dots and a superscripted two negative sign.;

(b)

Two Lewis structures are shown. The left shows the symbol A l with a superscripted three positive sign while the right shows the symbol O surrounded by eight dots and a superscripted two negative sign.;

(c)

Two Lewis structures are shown. The left shows the symbol G a with a superscripted three positive sign while the right shows the symbol C l surrounded by eight dots and a superscripted negative sign.;

(d)

Two Lewis structures are shown. The left shows the symbol K with a superscripted positive sign while the right shows the symbol O surrounded by eight dots and a superscripted two negative sign.>;

(e)

Two Lewis structures are shown. The left shows the symbol L i with a superscripted positive sign while the right shows the symbol N surrounded by eight dots and a superscripted three negative sign.;

(f)

Two Lewis structures are shown. The left shows the symbol K with a superscripted positive sign while the right shows the symbol F surrounded by eight dots and a superscripted negative sign.

5.
A Lewis diagram shows two phosphorus atoms triple bonded together each with one lone electron pair.

vii. (a)
A Lewis structure shows two oxygen atoms double bonded together, and each has two lone pairs of electrons.

In this instance, the Lewis construction is inadequate to draw the fact that experimental studies have shown two unpaired electrons in each oxygen molecule.

(b)

A Lewis structure shows a carbon atom that is single bonded to two hydrogen atoms and double bonded to an oxygen atom. The oxygen atom has two lone pairs of electrons.;

(c)

A Lewis structure shows an arsenic atom single bonded to three fluorine atoms. Each fluorine atom has a lone pair of electrons.;

(d)

A Lewis structure shows a nitrogen atom with a lone pair of electrons single bonded to a chlorine atom that has three lone pairs of electrons. The nitrogen is also double bonded to an oxygen which has two lone pairs of electrons. ;

(e)

A Lewis structure shows a silicon atom that is single bonded to four chlorine atoms. Each chlorine atom has three lone pairs of electrons.;

(f)

A Lewis structure shows an oxygen atom with a lone pair of electrons single bonded to three hydrogen atoms. The structure is surrounded by brackets with a superscripted positive sign.;

(thou)

A Lewis structure shows a nitrogen atom single bonded to four hydrogen atoms. The structure is surrounded by brackets with a superscripted positive sign.;

(h)

A Lewis structure shows a boron atom single bonded to four fluorine atoms. Each fluorine atom has three lone pairs of electrons. The structure is surrounded by brackets with a superscripted negative sign.;

(i)

A Lewis structure shows two carbon atoms that are triple bonded together. Each carbon is also single bonded to a hydrogen atom.;

(j)

A Lewis structure shows a carbon atom that is triple bonded to a nitrogen atom that has one lone pair of electrons. The carbon is also single bonded to a chlorine atom that has three lone pairs of electrons.;

(k)

A Lewis structure shows two carbon atoms joined with a triple bond. A superscripted 2 positive sign lies to the right of the second carbon.

9. (a) SeFhalf-dozen:
A Lewis structure shows a selenium atom single bonded to six fluorine atoms, each with three lone pairs of electrons.;

(b) XeF4:

A Lewis structure shows a xenon atom with two lone pairs of electrons. It is single bonded to four fluorine atoms each with three lone pairs of electrons.;

(c) SeCl3 +:

A Lewis structure shows a selenium atom with one lone pair of electrons single bonded to three chlorine atoms each with three lone pairs of electrons. The whole structure is surrounded by brackets.;

(d) Cl2BBCl2:

A Lewis structure shows two boron atoms that are single bonded together. Each is also single bonded to two chlorine atoms that both have three lone pairs of electrons.

11. 2 valence electrons per Lead atom are transferred to Cl atoms; the resulting Pb2+ ion has a 6s two valence trounce configuration. Two of the valence electrons in the HCl molecule are shared, and the other half dozen are located on the Cl atom as lone pairs of electrons.

13.
Two reactions are shown using Lewis structures. The top reaction shows a carbon atom, single bonded to three hydrogen atoms and single bonded to an oxygen atom with two lone pairs of electrons. The oxygen atom is also bonded to a hydrogen atom. This is followed by a plus sign and the number one point five, followed by two oxygen atoms bonded together with a double bond and each with two lone pairs of electrons. A right-facing arrow leads to a carbon atom that is double bonded to two oxygen atoms, each of which has two lone pairs of electrons. This structure is followed by a plus sign, a number two, and a structure made up of an oxygen with two lone pairs of electrons single bonded to two hydrogen atoms. The bottom reaction shows a carbon atom, single bonded to three hydrogen atoms and single bonded to another carbon atom. The second carbon atom is single bonded to two hydrogen atoms and one oxygen atom with two lone pairs of electrons. The oxygen atom is also bonded to a hydrogen atom. This is followed by a plus sign and the number three, followed by two oxygen atoms bonded together with a double bond. Each oxygen atom has two lone pairs of electrons. A right-facing arrow leads to a number two and a carbon atom that is double bonded to two oxygen atoms, each of which has two lone pairs of electrons. This structure is followed by a plus sign, a number three, and a structure made up of an oxygen with two lone pairs of electrons single bonded to two hydrogen atoms.

15.
Two Lewis structures are shown. The left depicts a carbon atom single bonded to four chlorine atoms, each with three lone pairs of electrons. The right shows a carbon atom double bonded to an oxygen atom that has two lone pairs of electrons. The carbon atom is also single bonded to two chlorine atoms, each of which has three lone pairs of electrons.

17. (a)
A Lewis structure is shown. A nitrogen atom is single bonded to two hydrogen atoms and a carbon atom. The carbon atom is single bonded to a hydrogen atom and two other carbon atoms. One of these carbon atoms is single bonded to two hydrogen atoms and an oxygen atom. The oxygen atom is bonded to a hydrogen atom. The other carbon is single bonded to two oxygen atoms, one of which is bonded to a hydrogen atom. The oxygen atoms have two lone pairs of electron dots, and the nitrogen atom has one lone pair of electron dots.;

(b)

A Lewis structure is shown. A nitrogen atom is single bonded to two hydrogen atoms and a carbon atom. The carbon atom is single bonded to an oxygen atom and one nitrogen atom. That nitrogen atom is then single bonded to two hydrogen atoms. The oxygen atom has two lone pairs of electron dots, and the nitrogen atoms have one lone pair of electron dots each.;

(c)

A Lewis structure is shown. A carbon atom is single bonded to three hydrogen atoms and a carbon atom. The carbon atom is single bonded to an oxygen atom and a third carbon atom. This carbon is then single bonded to two oxygen atoms, one of which is single bonded to a hydrogen atom. Each oxygen atom has two lone pairs of electron dots.;

(d)

A Lewis hexagonal ring structure is shown. From the top of the ring, three carbon atoms, one nitrogen atom, a carbon atom and a nitrogen atom are single bonded to one another. The top carbon is single bonded to an oxygen, the second and third carbons and the nitrogen atom are each single bonded to a hydrogen atom. The next carbon is single bonded to an oxygen atom and the last nitrogen is single bonded to a hydrogen atom. The oxygen atoms have two lone pairs of electron dots, and the nitrogen atoms have one lone pair of electron dots.;

(e)

A Lewis structure is shown. A carbon atom is single bonded to three oxygen atoms. Two of those oxygen atoms are each single bonded to a hydrogen atom. Each oxygen atom has two lone pairs of electron dots.

xix.
A Lewis structure is shown. A carbon atom is single bonded to three hydrogen atoms and another carbon atom. The second carbon atom is double bonded to another carbon atom and single bonded to a hydrogen atom. The last carbon is single bonded to two hydrogen atoms.

21. Each bail includes a sharing of electrons between atoms. Two electrons are shared in a single bond; four electrons are shared in a double bond; and six electrons are shared in a triple bond.

Source: https://opentextbc.ca/chemistry/chapter/7-3-lewis-symbols-and-structures/

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