The number of neutrons, protons and electrons are 16, 16 and 18 respectively, the symbol of the species is:

The atomic number is equal to number of protons = 16.

The element is S.

Atomic mass number  = 

number of protons + number of neutrons 

= 16 + 16 = 32. 

The species is not neutral as the number of protons is not equal to number of electrons. It is negatively charged with charge equal to excess of electrons 

= 18 – 16 = 2. 

 The symbol of the species is ${}_{16}{}^{32}\mathrm{S}^{2-}$