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 positive 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

(i) F (fluorine) exhibits only +ve oxidation state (+1) its compounds because it is the most electronegative element.
(ii) Cs (cesium) exhibits only+ve oxidation state (+1) its compounds because it is the most electropositive element.
(iii) Iodine has seven electrons in the valance shell as well as vacant 5d orbital to which electrons from 5PO and 5s orbitals can be shifted.Therefore, the elements exhibits- 1 oxidation state as well as variable positive oxidation states of +1,+3,+5 and +7 in its compounds.
(iv) Ne (neon) neither exhibits +ve nor-ve oxidation states because it is a noble gas element with completely filled orbitals `(1s^(2)2s^(2)2P^(6))`.Moreover, it has no vacant d-orbitals