Salts of indium(III) are used in some nutritional supplements, despite known side effects, because it is claimed that they can enhance the speed of memory, balance hormones, and reduce the need for sleep. However, indium (I) salts are unstable in water and so cannot be used in the diet. If you were working in a pharmaceutical laboratory, you would need to be able to distinguish the properties of these two ions. Write the electron configurations of

(a) In 1 and

(b) In³⁺.

ANTICIPATE Because indium, In, is in Group 13, with the “generic” electron configuration [core]s²p¹, you should expect successive loss of the p-electron and then the two s-electrons to give the configurations [core]s² and [core], respectively.

PLAN Identify the configuration of the neutral atom from its position in the periodic table. Remove electrons from the valence-shell p-orbitals first, then from the s-orbitals, and finally, if necessary, from the d-orbitals in the next-lower shell, until the number of electrons removed equals the charge on the ion.