As per the rule, oxidation number of alkaline earth metals in their compounds is +2. Oxidation number of oxygen in it's compounds is -2(except peroxides) and the sum of oxidation numbers of all the elements of a neutral compound is zero.
Each one is a living organism.
Depends on the element it can by up to 3, 8, or maybe 16.
I think maybe reptiles bu i could be wrong. :)
