Chapter 6 - Ionic and Molecular Compounds - 6.3 Naming and Writing Ionic Formulas - Questions and Problems - Page 195: 6.24

a. $Fe^{2+}$ b. $Cr^+$ c. $Ni^{3+}$ d. $Al^+$

You can find the answers to this question on page 185, topic 'Positive ions: Loss of electrons'. A cation is a type of ion that loses valence electrons and has a positive charge. The charge of a cation is determined by the number of electrons lost by the element.