Answer:
(A) A metal that lost three electrons - (b) Z³⁺
(B) A nonmetal that gained one electron - (d) X⁻
(C) A metal that lost one electron - (c) Y⁺
(D) A nonmetal that gained three electrons - (a) V³⁻
Step-by-step explanation:
Oxidation is described as the loss of electrons by a species. Oxidation increases the oxidation number of the species.
Reduction is described as the gain of electrons by a species. Reduction decreases the oxidation number of the species.
The oxidation number of an ionic species is equal to the charge on that ionic species.
Therefore, when a neutral atom gains electrons, its oxidation state is negative, and when it loses electrons, its oxidation state is positive.
(A) A metal that lost three electrons - (b) Z³⁺
When a neutral metal (Z) loses three electrons and gets oxidized, the metal gets oxidized from 0 to +3 oxidation state.
Z → Z³⁺ + 3 e⁻
(B) A nonmetal that gained one electron - (d) X⁻
When a neutral metal (X) gains one electron and gets reduced, the metal gets reduced from 0 to -1 oxidation state.
X + e⁻ → X⁻
(C) A metal that lost one electron - (c) Y⁺
When a neutral metal (Y) loses one electron and gets oxidized, the metal gets oxidized from 0 to +1 oxidation state.
Y → Y⁺ + e⁻
(D) A nonmetal that gained three electrons - (a) V³⁻
When a neutral metal (V) gains three electrons and gets reduced, the metal gets reduced from 0 to -3 oxidation state.
V + 3 e⁻ → V³⁻