The horizontal rows are called periods and vertical columns are called groups.
is called the periodic table because the properties of elements depend on atomic mass and
Moseley's Periodic Law, the properties of elements are periodic function of atomic number.
In theelectron current periodic table are ordered by atomic number.
The elements of a same group have the same outer electron configuration and chemical properties
The components of the same period have the same number of levels of electrons and that amount
coincides with the period number.
Inert gases have their last full level (with exceptions) and are chemically inactive.