http://www.ck12.org Chapter 9. Covalent Bonding
Adouble covalent bondis a covalent bond formed by atoms that share two pairs of electrons. The double covalent
bond that occurs between the two carbon atoms in ethene can also be represented by a structural formula or a
molecular model, as pictured below (Figure9.4).
FIGURE 9.4
(A) The structural model for C 2 H 4 consists
of a double covalent bond between the
two carbon atoms and single bonds to
each of the hydrogen atoms. (B) Molec-
ular model of C 2 H 4.Similarly, atriple covalent bondis a covalent bond formed by atoms that share three pairs of electrons. In its pure
form, the element nitrogen exists as a diatomic gas. The majority of Earth’s atmosphere is made up of N 2 molecules
(Figure9.5). A nitrogen atom has five valence electrons, which can be shown as one pair and three unpaired
electrons. When combining with another nitrogen atom to form a diatomic molecule, the three single electrons on
each atom combine to form three shared pairs of electrons.
FIGURE 9.5
Each nitrogen atom has one lone pair of electrons and six electrons that are shared with the other atom, so each atom
obeys the octet rule.
Practice Problems- Draw Lewis electron dot structures for the molecules below, each of which contains one or more multiple
covalent bonds.
(a) CO 2
(b) C 2 H 2