Chapter EH, Problem 5R

Solution

Interpretation: To determine the reason why hydrogen element is not placed in group 17.

Concept Introduction: The elements which have 7 valence electrons and need only one electron to complete their octet, are named group 17 elements.

Hydrogen would be placed in group 1 because it has identical properties to alkali metals.

The atomic number of hydrogens is 1 and its electronic configuration will be ${\text{1s}}^{\text{1}}$ . The electronic configuration is comparable to alkali metals. It has one valence electron; hence, it will place in group 1 in the periodic table. Group 17 elements have 7 valence electrons, but hydrogen has only one valence electron.

The chemical property of the hydrogen atom is identical to group 1.

• Hydrogen will be less reactive but halogens are very reactive.
• Hydrogen has lesser electron affinity than halogens.