Question

Question 31
“Hydrogen occupies a unique position in Modern Periodic Table”. Justify the statement.

Answer 1

Hydrogen occupies a unique position in the modern periodic table due to the following reasons:

i) Both hydrogen and alkali metals have a similar outer electronic configuration as both have one electron in the valence shell. Therefore, some of the properties of hydrogen are similar to those of alkali metals hence, it shall be placed in group 1 along with alkali metals.
ii) Both hydrogen and halogens have a similar outer electronic configuration (both have one electron less than the nearest inert gas configuration). Therefore, some of the properties of hydrogen are similar to halogens and hence, it can also be placed in the group 17 along with halogens.

In some properties, it differs from both alkali metals and halogens. For example, the oxide of hydrogen, that is, ${\text{H}}_2\text{O}$ is neutral but the oxides of alkali metals are basic while those of halogens are acidic.