Dot and cross diagram for oxygen ion

Explanation:

We can use dot and cross diagrams to show how a pair of electrons forms a covalent bond.

Here is the dot and cross diagram for oxygen (O2), a diatomic molecule. Notice the lone pairs of electrons and the two shared pairs of electrons.

There are different kinds of covalent bonds:

a single covalent bond is when two atoms share a single pair of electrons. Represented by a single line (–).

a double covalent bond is when two atoms share two pairs of electrons. Represented by a double line (＝).

a triple covalent bond is when two atoms share three pairs of electrons. Represented by a triple line (≡).

the answer is d. 74.02