Why is hydrogen included in the metal activity series?

1 Answer

Although it is nonmetallic, hydrogen atoms do have some characteristics which make them behave like alkali metals in some chemical reactions.


Hydrogen has only 1 electron in its #1s# orbital, so its electronic structure closely resembles that of the other alkali metals, which have a single valence electron in a #2s, 3s, 4s...# orbital.

You might argue that hydrogen is missing only one electron from having a complete valence shell, and that it should be listed in Group VII with the halogen atoms (F, Cl, Br, etc.). This would be valid, too.

However, halogens are extremely electronegative, with F leading the way, and H is not very electronegative, so its chemical properties more closely resemble the alkali metals than the halogens, even though it does not form a true metal (except perhaps at extremely high pressures).

That's why the element hydrogen occupies a place in Group I rather than Group VII in the Periodic Table of Elements.

The video below summarizes an experiment to compare the activity of three metals; zinc, copper and magnesium. Any metal which react with acid (HCl in the video) are placed higher than hydrogen on the activity series, and the metals which do not react with acids would be placed below hydrogen on the series.

video from:Noel Pauller

Hope this helps!