Question

Which of the following halide ions is easily oxidized?
A.${{\text{F}}^{\text{ - }}}$
B.${\text{B}}{{\text{r}}^{\text{ - }}}$
C.${{\text{I}}^{\text{ - }}}$
D.${\text{C}}{{\text{l}}^{\text{ - }}}$

Answer 1

Oxidation means loss of electrons or reaction with oxygen. An atom or an ion will get oxidized only when it either has an excess of electrons or it can attain stability by losing electrons. Other factors that affect the loss of electrons are diffused orbitals that are not strong enough to hold on to the electrons. The halide ion with weak effective nuclear charge on its valence shell shall get oxidised easily.

Complete step by step answer:
The order of atomic size or ionic size of the elements in group 17 is as follows: ${{\text{I}}^ - } > {\text{B}}{{\text{r}}^ - } > {\text{C}}{{\text{l}}^ - } > {{\text{F}}^ - }$
As the size of the atoms increase the distance of the electrons from the nucleus increases and so the attraction of the nucleus over the valence shell electrons decrease and the electrons are easily lost and the atoms are easily oxidized.
Hence, the most easily oxidizable ion in the above anions is ${{\text{I}}^{\text{ - }}}$.

Thus, the correct answer is option C.

Note:
The ability of an element to get oxidized is based on the oxidation potential of the elements and there is a list of elements for that. The reduction is the opposite of oxidation and involves gain of electrons. In the periodic table the metals are easily oxidisable and the oxidation potential decreases down the group while the reduction potential increases down the group. Along the period in the periodic table, the oxidation potential decreases while the reduction potential increases. Hence the alkali metals act as good reducing agents while the halogens act as good oxidising agents.