Hydrogen is the first element of the periodic table. It was discovered by Cavendish and named by Lavoisier.
Hydrogen belongs to the first group and the first period of the periodic table. Although the properties of hydrogen should be similar to those of the other members of the first group, this is not the case.
Some of the properties of hydrogen resemble the properties of Group IA elements (Alkali metals), and some of the properties resemble the properties of Halogens (VIIA).
Thus, hydrogen was put at the top of the periodic table so that the symmetry of the modern periodic
the table is not disturbed.