Question

A compound contains atoms of three elements A, B and C. If the oxidation number of A is +2, B is +5 and that of C is -2, the possible formula of the compound is
A.${A_3}{(B{C_4})_2}$
B.${A_3}{({B_4}C)_2}$
C.$AB{C_2}$
D.${A_2}{(B{C_3})_2}$

Answer 1

Hint:Oxidation number or also called the oxidation state is the number of electrons that an atom either loses or gains in order to form a chemical bond. It plays a very important role in determining the shape, geometry and nomenclature of a compound. A compound is always neutral.

Complete step by step answer:
We know that the oxidation number of a compound is the number of electrons gained or lost to form chemical bonds with other atoms; it is the degree of oxidation of an atom. Some important points to remember are that
Oxidation number of a free element is zero.
The oxidation number of hydrogen is +1 but it is taken as -1 if it reacts with a less electronegative element.
The oxidation number of oxygen is -2 but it is taken as -1 in terms of peroxides.
Similarly different groups of the periodic table have their oxidation number depending on their electron activity.
Oxidation numbers may be positive, negative or zero.
In this question we see that there are three elements A, B and C given to us with oxidation states as +2, +5 and -2.
We know that the general formula of the compound with these three elements will be ${A_X}{B_Y}{C_Z}$ where X, Y, Z are the atomicity of the atom.
So, we know that a compound is always neutral and so the oxidation number of the compound will be zero
$\therefore 2x + 5y - 2z = 0$
The maximum oxidation state cannot exceed +8 or -3 because that will be the maximum electron gain and lose from the orbital, so we use hit and trial method and we find that
(x,y,z) can be taken as either (1,2,6) or (3,2,8) according to the solution of the equation formed.
So, the formula of the compound can be written as $A{(B{C_3})_2}$ or ${A_3}{B_2}{C_8}$ .
Thus, the correct answer is option (A)
${A_3}{(B{C_4})_2}$

Note:
The highest oxidation state of nonmetals is equal to the total number of electrons present in its valence shell and add a plus sign to it as it indicates the available electrons. The sum of the oxidation states of all the atoms in an ion is taken equal to the charge on the ion.