Which chemical formula shows an ionic compound?

Responses

NaCl
upper case N lower case a upper case C lower case l

CO2

upper case C O subscript 2

C6H12O6

upper case C subscript 6 end subscript upper case H subscript 12 end subscript upper case O subscript 6 end subscript

N2O

upper case N subscript 2 end subscript upper case O