Which property of an atom determines what other elements it reacts with?

A. The number of valence electrons

B. The mass of the atom

C. The number of protons in the nucleus

D. The number of neutrons in the nucleus

A. The number of valence electrons determines how it reacts with other elements.

One to three valence electrons: The element behaves like a metal and reacts with non-metals.

Five to seven valence electrons: The element behaves like a non-metal and reacts with metals.

Four valence electrons: Elements at the top of the Group are non-metals, while those at the bottom are metals.

Eight valence electrons: Elements have a complete octet, so they are generally unreactive.