Question 4.3: Give the chemical symbol for each of the following ions. a. ......

a. A neutral barium atom contains 56 protons and 56 electrons because barium has an atomic number of 56. The barium ion formed by the loss of 2 electrons would still contain 56 protons but would have only 54 electrons because 2 electrons were lost.
\quad\quad\quad\quad56 protons = 56 + charges
\quad\quad\quad\quad \underline{54  electrons = 54  –  charges}
\quad\quad\quad\quad Net charge = 2+
The chemical symbol of the barium ion is thus Ba^{2+}.
b. The atomic number of phosphorus is 15. Thus 15 protons and 15 electrons are present in a neutral phosphorus atom. A gain of 3 electrons raises the electron count to 18.
\quad\quad\quad\quad15 protons = 15 + charges
\quad\quad\quad\quad \underline{18  electrons = 18  –  charges}
\quad\quad\quad\quad Net charge = 3-
The chemical symbol for the ion is P^{3-}.