Question

Which chemical symbol represents an element?
Responses

C20

uppercase C subscript 20 end subscript

H2O

uppercase H subscript 2 end subscript uppercase O

CO

uppercase C uppercase O

H2CO3

uppercase H subscript 2 end subscript uppercase C O subscript 3 end subscript

Answer 1

None of the choices is a proper element symbol.

- H2O and H2CO3 are chemical formulas for compounds (water and carbonic acid).
- C20 denotes a cluster/molecule of 20 carbon atoms, not a single-element symbol.
- CO (both letters uppercase) is the molecular formula for carbon monoxide; the element symbol for cobalt is Co (capital C, lowercase o).