See the attached file.
Elements react with each other to change the number of valence electrons that they have. Elements react differently depending on the number of valence electrons in the element.
For the most part, elements want to have 8 valence electrons. This rule is known as the octet rule. The noble gases are unreactive because all of them have 8 valence electrons and the elements are stable.
There are a few exceptions to the octet rule. Hydrogen and helium want to have 2 valence electrons. Also, boron is stable with 6 valence ...
This 407 word solution provides a detailed explanation regarding finding the oxidation states of various elements. Included is an explanation of the octet rule, the difference between metals and non-metals regarding their oxidation states, and an introduction and summary of the material for ease of understanding.