multiple bond in covalent
TRANSCRIPT
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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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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)
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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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General, Organic, and Biological Chemistry Copyright 2010 Pearson Education, Inc.8
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
13
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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