The Periodic Table

The periodic table is an arrangement of elements in order of increasing atomic number. The atomic number tells you the number of protons in the atom and the mass number tells you the total number of protons and neutron in the nucleus of the atom. In the periodic table the horizontal rows are called the periods and the vertical columns are called a group or family of elements. The first column on the left of the table is called the alkali metal family which has six elements. The right-most column is called the noble gas family with very unreactive elements. On the left of the noble gases is the halogen family consisting of highly reactive elements.