What is the valence number of an atom?

The valence number of an atom refers to the number of unpaired electrons in the valence shell. This is significant because these unpaired electrons are what participate in chemical bonding, allowing the atom to form bonds with other atoms to create molecules. The valence electrons determine the chemical reactivity and the type of bonds that an atom can make, whether they be covalent, ionic, or metallic.

Atoms seek to achieve a full valence shell (often resembling the electron configuration of the nearest noble gas), which is typically stable. Because of this, the number of unpaired electrons directly influences how an atom interacts with others during chemical reactions. For example, an atom with one unpaired electron is likely to form one bond, while an atom with four unpaired electrons can form four bonds.

The other options do not accurately describe the valence number:

• The number of protons in the nucleus is the atomic number and determines the identity of the element, not its bonding capacity.
• The total number of electrons includes both filled and unfilled shells, which does not reflect the atom’s bonding behavior.
• The number of neutrons present in an atom relates more to the atom's isotopes and overall mass rather than its capacity to bond with other