Final answer:
Elements in the same column of the periodic table have similar characteristics because they have the same number of valence electrons, which determine their chemical behavior.
Step-by-step explanation:
The arrangement of elements on the periodic table is based on their electron configurations. Elements in the same column, or group, of the periodic table have similar characteristics because they have the same number of valence electrons. Valence electrons are the electrons in the outermost energy level of an atom, and they determine the chemical behavior of an element.
For example, elements in Group 1 of the periodic table, such as hydrogen, lithium, and sodium, all have one valence electron in their outermost energy level. This makes them highly reactive and prone to losing that electron to form positive ions.
Similarly, elements in Group 17, such as fluorine, chlorine, and bromine, all have seven valence electrons. They tend to gain one electron to achieve a full outermost energy level and become negatively charged ions.