It means it's the anion or the negatively charged atom
Explanation:
I) carbon dioxide
ii) nitrogen dioxide
iii) nitric acid
iv) sulphric acid
v) Potassium dichromate
vi) hexacyanoferrate (III) ion( not sure)
Answer:
a) Sulphur + Oxygen → Sulphur dioxide
b) Carbon + Oxygen → Carbon dioxide
c) Sulphur + Iron → Iron sulphide
I think it’s C but I’m not sure