Which of the following molecules is formed by single bonds alone?

F2

O2

CO

N2

O3

The F₂ molecule is formed by single bonds alone.

Explanation:

The octate rule dictates that atoms have a preference to have 8 electrons in their valence shells. Considering this rule we can analyse how the electrons are distributed in the molecules and see how the atoms bond to obbey the rule.

The fluorine atom has 7 electrons in its valence shell. This means that it needs one more electron to reach stability. Therefore, when two fluorine atoms combine, they share one electron each, forming a single bond.

The atoms of the other molecules need more than one electron to reach the octate, therefore they need to share more electrons, forming double and triple bonds.