Question

Nonmetallic elements form ions by _____ valence electrons to complete their outer shell.

Answer 1

Answer: Non-metals form ions when they gain electrons.

Explanation:

An ion is formed when an atom looses or gains electron.

• When an atom looses electrons, it will form a positive ion known as cation.
• When an atom gains electrons, it will form a negative ion known as anion.

Metals are the elements which have a tendency to loose electrons and thus they form cations. Example: Sodium will loose 1 electron to form $Na^+$ ion.

Non-metals are the elements which have a tendency to gain electrons and thus they form anions. Example: Fluorine will gain 1 electron to form $F^-$ ion.

Hence, non-metals form ions when they gain electrons.