Graduation of elements in the periodic table
 

I would like to know why are there only two elements in period one of the periodic table,while there are 8 and more in other groups? Confused,Mr N.S Nxumalo in S.A

From left to right, you are adding one electron per element. When you reach the end of a period, you have filled up an electron shell. A full electron shell means the atom is especially stable and you have a noble gas. The very first electron shell can only hold two electrons. The rest can all hold more. This means in period one you only need two electrons to fill the electron shell. So the second element is a noble gas.