question_answer 1)

Justify the position of hydrogen in the periodic table on the basis of its electronic configuration.

Answer:

The electronic configuration of hydrogen is\[\mathbf{1}{{\mathbf{s}}^{\mathbf{1}}}\]. Like alkali metals, it has one electron in the outermost energy shell\[Li(3),1{{s}^{2}},2{{s}^{1}};Na(11),1{{s}^{2}},2{{s}^{2}},2{{p}^{6}},\mathbf{3}{{s}^{1}}K(19)[Ar]\mathbf{4}{{s}^{1}}\]Thus, hydrogen is placed above lithium in the first period and first group as it behaves as electropositive like alkali metals on account of similar outer shell configuration. Halogens have seven electrons in the outermost energy shell, i.e., one electron less than next noble gas. For example, One electron less than next noble gas, i.e., neon. \[F(9)1{{s}^{2}},2{{s}^{2}}2{{p}^{5}}\]One electron less than next noble gas, i.e., argon. Similarly, hydrogen has one electron in the outermost shell, i.e., one electron short than next noble gas, i.e., helium. Thus, hydrogen can also be placed above fluorine in the first period and group 17 as it behaves as electronegative like halogens on account of similar outer configuration. Hence, hydrogen has no fixed position in periodic table on account of its electronic configuration.