Question

H is much reactive than amolecule of hydrogen. why

Answer 1

Atomic hydrogen it has one valence electron, whereas molecular hydrogen has none. In chemistry in order for an element or a molecule to be stable (non - reactive) it must satisfy the Octet Rule, where an atom has 8 valence electrons in its outer shell (or 2 for molecular hydrogen and helium).

So in atomic hydrogen, that atom wants to rid of that lonely electron so it can be stable. Hydrogen is classified in group 1, any element in group 1 is highly reactive, this is due to the lone electrons they all have.

Molecular hydrogen on the other hand is two hydrogen atoms bonded together. They share their two electrons and this satisfies the quantum principle number. It fills the 1s orbital with two electrons and it gives molecular hydrogen the electronic configuration of helium.

Hope this helps!!

Answer 2

heya!
here's your answer!
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hydrogen is a very reactive reducing agent but its molecule is non reactive because of the simple reason that hydrogen moleculw is made up of two atoms of hydrogen hence it acquires a stable position.

where is the hydrogen atom is unstable as it needs to complete its Duplex in the valence shell to become stable which it hasn't completed yet there for hydrogen atom which hasn't completed its duplet is reactive

and a hydrogen molecule which has the chemical formula H2 is unreactive because it is stable.

Hope this helps you:)