What is the correct symbol of an ion containing 17 protons, 20 neutrons and 18 electrons

The symbol of the ion is A^-

Explanation:

Let A be the symbol of the element.

Proton = 17

Electron = 18

Neutron = 20

Since the element has more electrons than protons, it means it has gain electrons.

From the question given,

The difference between the electron and proton = 18 - 17 = 1

So, the element has gain 1 electron.

Therefore the symbol of the ion is A^-