what is the oxidation number for selenium? and what is an oxidation # ?

Question

it's for a science project.

Answer 1

Selenium (Se) is in Group 6 below Oxygen & Sulphur. Being in Group 6 it can have up to 6 electrons in volved in bonding hence its oxidation number is a maximum of 6. However, Se has two smaller oxidation numbers viz. 2 and 4, in these two cases only '2' or '4' electrons are involved in bonding. So altogether it can exhibit three oxidation numbers 2,4 & 6.
An Oxidation State is the number of electrons involved in bonding.
The highest oxidation state of an element is usually the group number.