What is the oxidation number for Mn in Mn2O7? (provide sign and number)

Answer;

+7

Explanation;

The sum of the oxidation numbers of all of the atoms in a neutral compound is 0. The sum of the oxidation numbers in a polyatomic ion is equal to the charge of the ion. In this case the overall oxidation number is Zero.

Thus; Oxidation number of oxygen is - 2

Mn2O7; has 2 manganese atoms and 7 oxygen atoms;

= (2 * y) + (7 * - 2) = 0

= 2y = 14

y = + 7

Oxidation number of Mn in Mn2O7 is + 7

The oxidation number of the elements should be equal to zero or the charge of the compound when summed together. In this case, the overall charge is zero. Oxygen has a charge of - 2, hence the magnesium ion should have a charge of + 7 in order for the overall charge to be equal to zero