* Molecule: A molecule is formed when two or more atoms bond together covalently. This means they share electrons.

* Compound: A compound is formed when two or more different elements bond together, usually through ionic bonding. This means one element donates an electron to another element, creating ions that are attracted to each other.

In the case of sodium chloride, sodium (Na) loses an electron to become a positively charged ion (Na+), and chlorine (Cl) gains an electron to become a negatively charged ion (Cl-). These oppositely charged ions are attracted to each other, forming the ionic compound NaCl.