The number of electrons , protons and neutrons in a species are equal to 18 , 16 and 16 respectively . Assign the proper symbol to the species .

Explanation

The atomic number is equal to number of The element is sulphur (S).
Atomic mass number = number of protons + number of neutrons = 16 + 16 = 32 .
Species is not neutral as the number of protons is not equal to electrons. It is anion (negatively charged) with charge equal to excess electrons = 18-16=2.
Symbol is `""_(16)^(32)S^(2-)`.
Note: Before using the notation `""_(2)^(A)X` find out whether the species is a neutral atom, a cation or an anion. If it is a neutral atom, Atomic number (Z) = number of protons in the nucleus of an atom = number of lectrons in a neutral atom is valid, i.e., number of protons = number of electrons = atomic number. If the species is an ion, determine whether the number of protons are larger (cation, positive ion) or smaller (anion, negative ion) than the number of electrons. Number of neutrons is always given by A-Z, whether the species is neutral or ion.