How to Find the Oxidation State & Ionic Charge of an Element
- 1). Examine the periodic table. You can easily see that neutral elements have a number of electrons equal to their atomic number. The charge on the atom is zero and the oxidation state is zero.
- 2). Find the possible ionic charges for each element, using the periodic table. The octet rule will indicate how many electrons each element requires to reach a stable electron configuration of eight electrons.
- 3). Balance the polyatomic ions to achieve the correct charge. Each element will potentially have a different charge. The oxidation state of the element is equal to its charge. For example, find the oxidation state and ionic charge of the elements in SO4^2- and MnO4^1. Oxygen needs two electrons to complete its octet. The oxidation state of O is (--II). The charge on the oxygen is -2. Using this to calculate the charge on the S and Mn yields SO4^-2. The charge on the ion is -2 and the expression x + 4 * (-2) = -2, therefore x = +6, and the charge on Mn is y + 4 * (-2) = -1, which equals +7.
- 4). Calculate the oxidation state of the element, which equals its charge. Following the example, S^+6 has an oxidation state of S(VI) and Mn^+7 has one of Mn(VII).
Source...