Question

What evidence supports putting hydrogen in Group 1Aof the periodic table? In some periodic tables, hydrogen is listed separately from all of the groups. In what ways is hydrogen, unlike a Group 1A element?

Short answer

Evidence that supports putting hydrogen in the Group of the periodic table -

It has $n{\text{s}}^{\text{1}}$ electron configuration, +1 cation, it forms many compounds with an oxidation state 1.

Hydrogen is unlike Group 1A as it is a hydride ion, it has diatomic ${\text{H}}_{\text{2}}$ molecules, it is a nonmetal, and forms covalent compounds.

Step-by-step solution

Electronic Configuration Definition

The distribution of electrons in atomic or molecular orbitals of an atom, molecule, or other physical structure is known as electron configuration.

Hydrogen in Group 1A

The simplest element known is hydrogen, whose most frequent atomic structure merely has one proton and one electron. H has a ${\text{1s}}^{\text{1}}$ ground-state electronic configuration. It resembles the alkali metals in that they can be oxidized to the ${\text{H}}^{\text{+}}$ion, which exists in aqueous solutions in the hydrated form. Also, hydrogen forms many compounds in which the oxidation state is +1 , as do the alkali metals.

Differentiating Hydrogen from Group  1A

On the other hand, hydrogen resembles halogens in that it forms a negative hydride ion (${\text{H}}^{\text{-}}$), which is isoelectronic with helium (${\text{1s}}^{\text{2}}$). Also, hydrogen forms diatomic${\text{H}}_{\text{2}}$molecules and is nonmetal.

Besides that, hydrogen is found in a large number of covalent compounds and it has the unique capacity for hydrogen-bond formation.

Therefore, Hydrogen is like Group 1A as it has $n{\text{s}}^{\text{1}}$ electron configuration, +1 cation, and many compounds with oxidation state 1. Also, hydrogen is unlike Group 1A as it is a hydride ion, it has diatomic ${\text{H}}_{\text{2}}$ molecules, it is a nonmetal, and forms covalent compounds.