Why are most metals found on the left side and center of the periodic table?

The placement of metals on the left side and center of the periodic table is fundamentally linked to their atomic structure and their tendency to lose valence electrons during chemical reactions.12

The primary chemical characteristic of a metal is its relatively low ionization energy, which is the energy required to remove an electron from an atom. Because metals have few electrons in their outermost shell, they tend to lose these electrons to form positive ions (cations).312

In contrast, elements on the right side of the periodic table—the nonmetals—possess higher ionization energies and higher electronegativity, meaning they are more likely to gain or share electrons to complete their valence shells.32

The periodic table is organized such that these properties follow predictable trends: ionization energy generally increases from left to right across a period. Consequently, the elements with the lowest ionization energies, which are the most chemically active metals, are located in the lower left-hand region of the table. The transition metals, located in the center, also share the metallic tendency to give up electrons, contributing to their classification as metals.31