Question

why as the position of hydrogen is not fixed in the Mentally periodic table

Answer 1

It is because hydrogen shows some properties of alkali metals in the first group and some properties of halogens in the 17th group in the Mendeleev's periodic table.

Answer 2

The position of H atom is not fixed in Mandeleev's periodic table due to the resemblance of H with many group in properties.

It resembles with alkali metals due to the properties like formation of cation, liberation of H2 gas at cathode etc.

It resembles with Carbon family as it has half the no. of electrones to complete octate.

It also resembles with halogens because it has one electron less to acquire noble gas configuration.

Due to this the position of H atom was not fixed.

Hope it helps.