# Question #8a6e5

Aug 9, 2014

Hydrogen is a nonmetal.

#### Explanation:

Hydrogen is in Group 1 of the Periodic Table, because it has the same $n {s}^{1}$ electron configuration as the alkali metals.

However, hydrogen differs from metals in several ways.

1. It is reluctant to form cations.

The alkali metals lose electrons easily to form cations.

But the ionization energy of hydrogen is 2.5 times that of lithium, the alkali metal with the highest ionization energy.

2. Elemental hydrogen consists of ${\text{H}}_{2}$ molecules.

Hydrogen atoms join by covalent bonds to form ${\text{H}}_{2}$ molecules.

The molecules are attracted to each other by weak London dispersion forces.

Metal atoms are attracted to each other by metallic bonds.

Molecules like ${\text{Na}}_{2}$ are so rare that they have been detected only by spectroscopic methods,

3. Hydrogen forms covalent compounds.

Examples are $\text{HCl}$ and ${\text{H"_2"SO}}_{4}$

The bonds in these compounds are covalent.

Most of the compounds of Group 1 metals are ionic.

For example, sodium chloride consists of ${\text{Na}}^{+}$ ions and ${\text{Cl}}^{-}$ ions.

4. Hydrogen forms hydride ions.

Hydrogen forms compounds like $\text{NaH}$, $\text{KH}$, and ${\text{CaH}}_{2}$.

In these compounds, the hydrogen exists as the hydride ion, ${\text{H}}^{-}$.

Compounds containing $\text{Na"^"-}$ and $\text{K"^"-}$ ions are rare.

However

Theoretical calculations predict that hydrogen can behave like a metal at a pressure of 500 000 atm.

It may exist as a metal in the interiors of large planets like Jupiter and Saturn.