Question

why hydrogen is such a special element so that we are unable to determine its position in periodic table??​

Answer 1

Hydrogen forms +1 ions and has one valence electron in an s orbital, which is a reason to put it in column 1 along with the alkali metals (even though it is not a metal). Hydrogen also forms -1 ions and is one electron short of a filled valence, which supports locating it in column 17 with the halogen.

Answer 2

if you glance at the periodic table, you will see hydrogen is the first element in the table. It is the smallest element on the table. It has atomic number one, which means it has only one electron orbiting it its shell. ... But they hydrogen atoms can also gain one electron similar to halogens.