Question

Which of the following elements shows only $+ 3$ oxidation state?
A) $B$
B) $Al$
C) $Ga$
D) $In$

Answer 1

As we know that all the given elements belong to thirteen having the electronic configuration as $n{s^2}n{p^1}$ and these elements possess three valence electrons in their outermost valence shell and the $+ 3$ oxidation state generally decreases down the group and $+ 1$ oxidation state increases.

Complete step by step solution:
As we know that oxidation state is basically defined as the degree of oxidation or in other terms the loss or gain of electrons of an atom in a chemical compound. It can be positive, negative and zero. We also are aware of the fact that the given elements Boron, Aluminium, Gallium and Indium belong to the group $IIIA$ of the periodic table containing $n{s^2}n{p^1}$ electronic configuration. In boron, $1{s^2}$electronic configuration shows its difference from aluminium and both aluminium and boron have noble gas kernels different from other four elements. The elements of this group contain three valence electrons in their outermost valence shell.
Among the group, Boron is the only element which shows only $+ 3$ oxidation state and other elements shows $+ 1$ oxidation state. Stability of $+ 3$ oxidation state decreases down the group due to inert pair effect and the $+ 1$ oxidation state usually increases.
Boron is used as a necessary mineral and affects the body having antioxidant properties and its compound which is boric acid can kill the yeast which causes vaginal infection in females.

Therefore, from the above explanation we can say that the correct answer is (A).

Note: Remember that Indium in $+ 1$ oxidation state is reducing agent and Gallium also exhibits a different oxidation state of $+ 2$. Boron possesses some medicinal properties and thus it is taken as boron supplements in medicines. It is also used for menstrual cramps, boron deficiency and vaginal yeast infections. It is also used for osteoporosis and osteoarthritis.