Oxidation Numbers and States

The video tutorial explains how to calculate oxidation numbers for calcium and hydrogen in the compound CaH2. It begins by stating that the sum of oxidation numbers in a compound is zero. Calcium, being in group two, has a +2 oxidation number. Consequently, hydrogen must have a -1 oxidation number in this compound, as it is paired with a metal, forming a hydride. The video concludes by summarizing the oxidation numbers for each element in calcium hydride.

What is the sum of oxidation numbers in a compound?

• Zero

• Always positive

• Depends on the compound

• Always negative

What is the oxidation number of calcium in CaH2?

• +2

• +1

• 0

• -2

If calcium has an oxidation number of +2, what must be the total oxidation number for hydrogen in CaH2?

• +2

• -1

• 0

• -2

What is the oxidation number of hydrogen in CaH2?

• -2

• +1

• 0

• -1

How does hydrogen's oxidation state change when it is combined with metals?

• It becomes zero

• It becomes negative

• It remains the same

• It becomes more positive