Question

Which of the following is the combining capacity of an element?
[A] Valency
[B] Oxidation number
[C] Oxidation capacity
[D] Both A and B.

Answer 1

Hint: The combining capacity of an element is the number of bonds it can form. It can form the bonds equal to the number of free electrons present in its outermost orbital. The correct answer here is a certain term that we use to define the electrons in the outermost shell.

Complete step by step answer:
To answer this question, let us discuss the terms mentioned in the options.
In the first option we have valency-
We know that in chemistry, valency is the combining power of an element with other elements which leads to the formation of chemical compounds or molecules. We determine the affinity or the combining power of an atom by the number of hydrogen atoms it combines with. For example, valency of oxygen in a water molecule is 2 as it combines with two hydrogen atoms.
According to IUPAC, valency is defined as- “The maximum number of univalent atoms (originally hydrogen or chlorine atoms) that may combine with an atom of the element under consideration, or with fragment, or for which an atom of this element can be substituted.”

In the second option we have oxidation number-
Oxidation number is the degree of oxidation i.e. number of electrons the atom of the considered element has lost in a chemical compound. We also refer to the oxidation number as oxidation state. It can be positive, negative or even zero.
According to IUPAC, oxidation state is defined as- “Oxidation state of an atom is the charge of this atom after ionic approximation of its hetero-nuclear bonds.”

And lastly, we have oxidation capacity-
We generally talk about oxidative capacity in biology as the measure of maximum capacity of muscles to use oxygen. It is the oxygen consumed in microliters per gram of the muscle per hour.
Also, the ability of the atmosphere to sustain enough OH concentration to remove current levels of hydrocarbons is known as the oxidation capacity of the atmosphere.
As we can see from the above discussion that valency is the measure of combining power of elements.
So, the correct answer is “Option A”.

Note: We often think that valency and oxidation number is the same thing but it is not. Oxidation number gives us the number of electrons the atom or molecule has gained or lost. Oxidation number can be positive or negative depending on the atom but valency is always positive. Valency and oxidation number can differ from each other due to difference in polarity of bonds.