21. Which of the following statements is true about ions? a. Cations form when an atom gains electrons
b. Cations form when an atom loses electrons
C. Anions form when an atom gains protons
d. Anions form when an atom loses protons

I think its B cause...

When an atom loses an electron, it becomes a cation (positive ion). When an atom gains an electron, it becomes an anion. Ions are created when an atom loses or gains an electron. Atoms can never lose or gain protons, as this would change the fundamental identity of the atom.

if I'm wrong...please don't attack me

intermolecular forces are the forces between molecules or particles.

there are two kinds of van der waals forces: weak london dispersion forces and stronger dipole-dipole forces.

in molecule of water there are dipole-dipole forces between negatively charged oxygen from one molecule of water and positively charger hydrogen of another molecule of water.

hydrogen bond is an electrostatic attraction between two polar groups that occurs when a hydrogen atom (h), covalently bound to a highly electronegative atom such as flourine (f), oxygen (o) and nitrogen (n) atoms.