The mass number of chlorine is 35 and atomic number is 17.

Number of neutrons is equal to the mass number - number of protons.

It means it has 35-17= 18 Neutrons.

Similarly, in case of carbon atomic number is 6 and its mass number is 12. hence, the number of protons is 6 and the number of neutrons is also 6.

Bromine has atomic number 35 which means it has 35 protons and 46 neutrons.