Chemistry: Atoms First (2nd Edition)

$^{151}_{63}$Eu$^{3+}$ $^{118}_{50}$Sn$^{2+}$
An ion with 63 protons, means that ion is that of an element that has atomic number 63, which is europium (Eu). We add 63 protons to 88 neutrons to get the mass number, which is 151. In a neutral atom, the number of electrons equals the number of protons. In this case, the number of protons and electrons are not equal; we have 63 protons but 60 electrons. Because we have three fewer electrons than protons, we have an ion with three fewer negative charges (3+). We write the mass number as a superscript to the left of the chemical symbol and the atomic number as a subscript also to the left of the chemical symbol. We write the charge of the ion as a superscript to the right of the chemical symbol. The complete symbol for this ion is $^{151}_{63}$Eu$^{3+}$. An ion with 50 protons means that the ion is that of an element that has atomic number 50, which is sulfur. We add 50 protons to 68 neutrons to get the mass number, which is 118. In a neutral atom, the number of electrons equals the number of protons. In this case, the number of protons and electrons are not equal; we have 50 protons but 48 electrons. Because we have two fewer electrons than protons, we have an ion with two extra positive charges (2+). We write the mass number as a superscript to the left of the chemical symbol and the atomic number as a subscript also to the left of the chemical symbol. We write the charge of the ion as a superscript to the right of the chemical symbol. The complete symbol for this ion is $^{118}_{50}$Sn$^{2+}$.