What type of covalent bond is
indicated by the four electrons, shown in green, in the center of the molecule? (A) A single covalent bond, (B) a
double covalent bond, or (C) a triple covalent bond.
Covalent bonds are chemical bonds
that are formed when two nonmetal atoms share one or more pairs of electrons. This definition tells us that at
least one pair of electrons is required to make a covalent bond. Since one pair of electrons is the
minimum requirement for a bond, a bond with one pair of electrons is a single
bond. Generally speaking, each atom will
donate one electron to form the bond.
We can see from the diagram that
there are four electrons involved in the oxygen–oxygen bond. Two of them are represented as
dots, and two are represented as crosses. The electrons in one oxygen atom
are represented by crosses, and the electrons in the other oxygen atom are
represented by dots. So, in this example, each atom has
donated two electrons. So there are two pairs of
electrons, thus four electrons in total. We call this a double bond. If three pairs of electrons,
totaling six electrons, were involved, then this would be a triple bond.
Since we have four electrons that
are being shared by two atoms, the type of bond is (B), a double covalent bond.