question_answer

Which of the elements Na, Mg, Si and P would have the greatest difference between the first and the second ionization enthalpies. Briefly explain your answer.

Answer:

                Among Na, Mg, Si and P, Na is an alkali metal. It has only one electron in the valence shell, therefore, its \[{{\Delta }_{i}}{{H}_{1}}\] is very low. However, after removal of one electron, it acquires neon gas configuration, i.e., \[N{{a}^{+}}(1{{s}^{2}}2{{s}^{2}}2{{p}^{6}})\]. Therefore, its \[{{\Delta }_{i}}{{H}_{2}}\] is expected to be very high. Consequently, the difference in first and second ionization enthalpies would be greatest in case of Na. However, it may be noted here that in case of Mg, Si and P, although their\[{{\Delta }_{i}}{{H}_{1}}\] will be much higher than that of Na but their \[{{\Delta }_{i}}{{H}_{2}}\] will be much lower than that of Na. As a result, the difference in their respective\[{{\Delta }_{i}}{{H}_{1}}\] and \[{{\Delta }_{i}}{{H}_{2}}\] would be much lower than that of Na.