Question

why is hydrogen placed in first group of periodic table​

Answer 1

because it has no fixed position.
it acts as an acid as well as base
It has atomic no 1
and atomic mass no 1
So, it is placed in the first group of periodic table

Answer 2

electronic configuration of hydrogen resembles that of alkali metals the alkali metals hydrogen combines with all the halogens Oxygen and sulphur to form compounds having similar formula .but just like halogens hydrogens also exist in diatomic molecules and it forms or combines with metals and nonmetals to form covalent compounds .

hydrogen has 1S orbitals so it can lose one electron like that of alkalis so it can be placed in the first group but also it forms hydrides like that of halogens so it can be placed with them also .Therefore it is placed separately in the first group and period of moderm periodic table.

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