Chapter 2
Chemistry Comes Alive
33
2
electron pairs, resulting in
double
or
triple covalent bonds
(Fig-
ure 2.7b and c). (Tese bonds are indicated by double or triple
connecting lines such as O
O or N
N.)
Polar and Nonpolar Molecules
In the covalent bonds we have
discussed, the shared electrons are shared equally between the
atoms of the molecule for the most part. Te molecules formed
molecule (CH
4
) is formed, carbon shares four pairs of electrons
with four hydrogen atoms (one pair with each hydrogen). Again,
the shared electrons orbit and “belong to” the whole molecule,
ensuring the stability of each atom.
When two atoms share one pair of electrons, a single cova-
lent bond is formed (indicated by a single line connecting the
atoms, such as H
¬
H). In some cases, atoms share two or three
O
O
O
O
or
Oxygen atom
Oxygen atom
Molecule of oxygen gas (O
2
)
O
O
(b) Formation of a double covalent bond: Two
oxygen atoms share two electron pairs.
+
N
N
N
N
or
Nitrogen atom
Nitrogen atom
Molecule of nitrogen gas (N
2
)
N
N
(c) Formation of a triple covalent bond: Two
nitrogen atoms share three electron pairs.
+
H
H
H
H
H
H
H
H
Hydrogen atoms
Carbon atom
Molecule of methane gas (CH
4
)
Structural formula
shows single bonds.
Structural formula
shows double bond.
Structural formula
shows triple bond.
(a) Formation of four single covalent bonds:
Carbon shares four electron pairs with four
hydrogen atoms.
or
C
H
H
H
H
C
C
Resulting molecules
Reacting atoms
+
Figure 2.7
Formation of covalent bonds.
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