Question

Oxidation states of X, Y and Z are +2, +5 and -2 respectively. Formula of the compound formed by these will be:
A. ${{X}_{2}}Y{{Z}_{6}}$
B. $X{{Y}_{2}}{{Z}_{6}}$
C. $X{{Y}_{5}}$
D. ${{X}_{3}}Y{{Z}_{4}}$

Answer 1

Oxidation number or state of an atom can be defined as the charge that an atom appears to have on forming ionic bonds with other heteroatoms. An atom which has higher electronegativity even if it forms a covalent bond is given a negative oxidation state.

Complete Solution :
Hence to find out which is the formula of the given compound we have to discuss all the options:
A.${{X}_{2}}Y{{Z}_{6}}$ by putting the values of oxidation states given we find this as,
$2\times 2 + 5 + ( -2\times 6) = 4 + 5 - 12 = -3$ but it should be zero so this is not the correct option.

B.$X{{Y}_{2}}{{Z}_{6}}$, now in this case put the values of oxidation states and the equation can be shown as:
$2 + 5\times 2 + (-2\times 6)=2 + 10 - 12 = 0$, so we can consider this option to be true.

C.$X{{Y}_{5}}$, putting the values in this case we find it is not equal to zero
$2 + 5\times 5 = 27$, so this is also not a correct option.

D.${{X}_{3}}Y{{Z}_{4}}$, put the values given in this case and we find that it comes
$2\times 3 + 5 + ( -2)\times 4 = 11 - 8 = 3$, so this is also not a correct option.
So we can consider that oxidation states of X, Y and Z are +2, +5 and -2 respectively. Formula of the compound formed by these will be $X{{Y}_{2}}{{Z}_{6}}$
So, the correct answer is “Option B”.

Note: The oxidation number is basically the count of electrons that atoms in a molecule can share, lose or gain while forming chemical bonds with other atoms of a different element. Larger the charge then it is difficult to remove an electron and so higher the ionization energy.