The elements fo groups 16 and 17 whose atoms have the largest negative electron gain enthalpies would be expected to form_________by gaining electrons to give___________configurations.

Options

A. polyatomic ions, noble gas
B. polyatomic ions, pseudo noble gas
C. monatomic ions, noble gas, or pseudo noble gas
D. monoatomic ions, noble gas

Answer

C

Explanation

An atom of a group 17 element (valence shell configuration `ns^2 np^5`) pics up one electron to give 1-anion `(ns^2 np^6)`, examples are `F^(-)` and `Cl^(-)`. Heavier halide ions (`Br^(-)` onwards) possess psudo-noble-gas configurations. Note that hydrogen also forms compounds of the 1-ion, `H^(-)`. The hydride ion `H^(-)` has a `1s^2` configuration, like the noble gas atom helium. An atom of a group 16 element (valence shell configuration `ns^2np^4`) picks up two electrons to give 2-anion `(ns^2np^6)`, examples are `O^(2-)` and `S^(2-)`.