Step-by-step explanation:
The element with atomic number of 33 is Arsenic (As)
ionized and found to have a charge of -3.
The negative sign denotes that it gained an electron. So -3 means it gained 3 electrons.
How many electrons in the atom?
Total number of electrons = Number of electrons gained + Electrons in it's neutral state
Total electrons = 3 + 33 = 36
What is the isotope symbol of this atom ?
As³⁻ it has the same number of electrons with Krypton (Kr)