multiple bond in covalent

7/28/2019 Multiple Bond in Covalent

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General, Organic, and Biological Chemistry Copyright 2010 Pearson Education, Inc. 1

Chapter 5

Compounds and Their Bonds

5.5

Covalent Compounds


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Covalent bonds form

when atoms share

electrons to complete

octets

between two nonmetal

atoms from from Groups

4A(14), 5A(15), 6A(16),

and 7A(17)

Covalent Bonds


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General, Organic, and Biological Chemistry Copyright 2010 Pearson Education, Inc.

Formation of H2

In the simplest covalent molecule, H2, the H

atoms

increase attraction as they move closer

share electrons form a covalent bond

3


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Formation of H2 (continued)

4


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Forming Octets in Molecules

In a fluorine (F2)molecule, each F atom

shares one electron

acquires an octet


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Diatomic Elements

These elements share

electrons to form diatomic,

covalent molecules.


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General, Organic, and Biological Chemistry Copyright 2010 Pearson Education, Inc.7

What is the name of each of the following

diatomic molecules?

H2 _______________

N2 _______________

Cl2 _______________

O2 _______________

I2 _______________

Learning Check


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What is the name of each of the following

diatomic molecules?

H2 hydrogen

N2 nitrogenCl2 chlorine

O2 oxygen

I2 iodine

Solution


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Carbon Forms 4 Covalent Bonds

In a methane (CH4) molecule,

the central C atom shares 4

electrons to attain an octet

each H atom shares 1

electron with the carbon

atom to become stable like

He


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In NH3, a N atom is bonded to three H atoms.

The electron-dot structure is written as:

Electron-Dot Formula for NH3

Lone pair of electrons


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Number of Covalent Bonds

The number of covalent bonds can be determined from

the number of electrons needed to complete an octet.


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Electron-Dot Formulas and Models

of Some Covalent Compounds


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Guide to Writing Electron-Dot

Formulas

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Guide to Writing Electron-Dot

Formulas

STEP 1 Determine the arrangement of atoms.

STEP 2 Determine the total number of valence

electrons.

STEP 3 Attach each bonded atom to the central atomwith a pair of electrons.

STEP 4 Place remaining electrons as lone pairs to

complete octets (2 for H atoms).

STEP 5 If octets are not complete, form a multiple bondby converting a lone pair to a bonding pair.


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Single and Multiple Bonds

In a single bond, one pair of electrons is shared.

In a double bond, two pairs of electrons are

shared.

In a triple bond, three pairs of electrons are

shared.


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Electron-Dot Formula of CS2

Write the electron-dot formula for CS2.

STEP 1 Determine the atom arrangement. The C atom

is the central atom.S C S

STEP 2Determine the total number of valence

electrons for 1C and 2S.

1 C(4e) + 2 S(6e) = 16e


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Electron-Dot Formula of CS2(continued)

STEP 3 Attach each S atom to the central C atom usingone electron pair.

S : C : S

16e 4e = 12e remaining

STEP 4 Attach 12 electrons as 6 lone pairs... ..

: S : C : S :


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Electron-Dot Formula of CS2(continued)

To complete octets, form one or more multiple bonds.

Convert two lone pairs to bonding pairs between C and

S atoms to make two double bonds.


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A Nitrogen Molecule has

A Triple Bond

In a nitrogen molecule, N2,

each N atom shares 3 electrons

each N atom attains an octet

the sharing of 3 sets of electrons is a multiple bondcalled a triple bond


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Resonance structures are

two or more electron-dot formulas for the same

arrangement of atoms

related by a double-headed arrow ( ) written by changing the location of a double bond

between the central atom and a different attached

atom

Resonance Structures


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Sulfur dioxide has two resonance structures.

STEP 1Write the arrangement of atoms.

O S O

STEP 2Determine the total number of valenceelectrons.

1 S(6e) + 2 O(6e) = 18e

STEP 3Connect bonded atoms by single electron pairs.

O : S : O 4e used

18e 4e = 14e remaining

Writing Resonance Structures


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STEP 4 Add 14 remaining electrons as 7 lone pairs.

STEP 5 Form a double bond to complete octets. Tworesonance structures are possible.

Writing Resonance Structures

(continued)


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FNO2, a rocket propellant, has two resonance structures.

One is shown below. What is the other resonance

structure?

Learning Check


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FNO2, a rocket propellant, has two resonancestructures. One is shown below. What is the otherresonance structure?

Solution

multiple bond in covalent

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