A molecule is a group of two or more atoms held together by chemical bonds, and it is electrically neutral.

Here's the breakdown for question 8:

A molecule is a group of two or more atoms held together by chemical bonds, and it is electrically neutral.
A radical (or polyatomic ion) is a group of atoms covalently bonded together that carries an overall electrical charge.

• $\text{HSO}_4^-$: This is a group of atoms with an overall negative charge. It is a radical.
• $\text{Cl}_2$: This consists of two chlorine atoms bonded together and is electrically neutral. It is a molecule.
• $\text{OH}^-$: This is a group of atoms with an overall negative charge. It is a radical.
• $\text{H}_2$: This consists of two hydrogen atoms bonded together and is electrically neutral. It is a molecule.
• $\text{CO}_3^{2-}$: This is a group of atoms with an overall negative charge. It is a radical.

Therefore:

• Molecules: $\boxed{\text{Cl}_2, \text{H}_2}$
• Radicals: $\boxed{\text{HSO}_4^-, \text{OH}^-, \text{CO}_3^{2-}}$