Why do metals form positive ions?

Metals form positive ions because they tend to lose electrons during chemical reactions, resulting in a positive charge.

In more detail, the formation of positive ions, also known as cations, is a fundamental characteristic of metals. This is primarily due to their atomic structure. Metals have a relatively small number of electrons in their outermost energy level, or valence shell. These electrons are relatively far from the nucleus and are not strongly attracted to it, making them relatively easy to remove.

During a chemical reaction, metals tend to lose these loosely held valence electrons. This process is known as oxidation. When a metal atom loses one or more electrons, it becomes a positively charged ion. The positive charge results from the fact that the metal atom now has more protons (which are positively charged) than electrons (which are negatively charged).

For example, sodium (Na), a metal, has one electron in its outermost shell. In a chemical reaction, it can easily lose this electron to become a sodium ion (Na+). Similarly, magnesium (Mg), another metal, has two electrons in its outermost shell. It can lose these two electrons to become a magnesium ion (Mg2+).

This tendency of metals to form positive ions is a key factor in their chemical behaviour. It explains, for example, why metals are good conductors of electricity (because the lost electrons can move freely and carry an electric charge), and why metals often react with non-metals (which tend to gain electrons and form negative ions).