Final answer:
In the periodic table, elements in the same column have the same number of valence electrons, which determine their chemical behavior. Elements with the same number of valence electrons exhibit similar chemical properties.
Step-by-step explanation:
In the periodic table of elements, elements in the same column have the same number of valence electrons. Valence electrons are the electrons in the outermost energy level of an atom that determine the atom's chemical behavior. These electrons are important because they are involved in chemical reactions, and elements with the same number of valence electrons exhibit similar chemical properties.
For example, elements in Group 1 of the periodic table (such as lithium and sodium) all have one valence electron. This makes them highly reactive and easily lose this electron to form positive ions.
The number of valence electrons can be determined by looking at the electron configuration of an atom. The electron configuration shows how the electrons are distributed in different energy levels and orbitals around the nucleus.