Consider the elements :
Cs ,Ne , I and F
(a) Identify the element that exhibits only negative oxidation state.
(b) Identify the element that exhibits only postive oxidation state.
(c) Identify the element that exhibits both positive and negative oxidation states.
(d) Identify the element which exhibits neither the negative nor does the positive oxidation state.

Explanation

a. `F`. Fluorine being the most electronegative element shows only a -ve oxidation atate of `-1`.
b. `Cs`. Alkali metals because of the presence of a single electron in the valence shell exhibit oxidation state of `+1`.
c. `I`. Because of the presence of seven electrons in the valence shell, I shows an oxidation state of `+1`, and because of the presence of d-orbitais it also exhibits `+ve` oxidation states of `+1, +3, +5` and `+7`.
d. `Ne`. It is an inert gas and hence it neither exhibits -ve nor +ve oxidation states.