Question

Which of the following elements would you expect to be most metallic? As Br Cl

Answer 1

The given elements belong to Group 17 i.e. halogen family. Most of the elements of this group are non-metallic in nature. But only As i.e Astatine is matallic in nature. The metallic character of any element is determined by the ionization energy of an element i.e. ease to remove electron from valence shell. Lower is the ionization energy, higher is the metallic character. Since these elements have outer shell electronic configration of ns2np5, they donot have tendency to losse electron instead they have very high affinity to gain electron, thus they are non - metallic in nature. But due to inert pair effect and large size of As, the ionization energy of As is low which makes it metallic in nature. Moreover, down the group ionization enegy decreases and thus metallic characcter increases down the group. Therefore order of metallic character is As>I>Br>Cl