An atom will form a chemical bond with another atom if 1. the other atom is identical to it.
2. their outer energy levels are already
filled.
3. ions can be formed.
4. the resulting molecule is more stable.

3. ions can be formed.

Explanation:

An atom will form a chemical bond with another atom if ions can be formed.

Ions are the charged atom or molecule (cation and anion) and are formed due to an imbalance between the number of protons and electrons between two different atoms. The chemical bond form between two atoms when electrons transfer from one atom to another atom. The atom that gains electrons becomes a negatively charged ion (anion) and the electron loses electron become cation, positively charged.

Hence, the correct answer is "3. ions can be formed."

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i believe the answer is a.