Which compound has the atom with the highest oxidation number?

a. cas

b. na3n

c. mgso3

d. al (no2) 3?

Answer is: c. MgSO₃.

In magnesium sulfite, magnesium has oxidation number + 2, sulfur has oxidatidion number + 4 and oxygen - 2:

+2 + (+4) + 3· (-2) = 0.

a) in calcium sulfide, calcium has oxidation number + 2 and sulfur - 2:

+2 + (-2) = 0.

b) in sodium nitride, sodium has oxidation number + 1 and nitrogen - 3:

3 · (+1) + (-3) = 0.

d) in aluminium nitrite, aluminium has oxidation number + 3, nitrogen + 3 and oxygen has - 2:

+3 + (+3 + 2 · (-2)) · 3 = 0.