Chlorine + Calcium --> Ionic Bond
Iron cannot covalently bond as it is a metal
Temperature, that's the most important factor
If the element is oxidized, then it's oxidation number would increase.
Let's say we have the following reaction.
2H2O --> O2 + 2H2
To the left, the oxidation number of O is -2, as it is bonded to two H, which is always H+. To the right, we have O2, and all gases have a oxidation number of 0 (zero). We say that O has been oxidized.
Answer:
The emmision of ionizing radiation or particles caused by the spontaneous disintegration of atomic nuclei
or
the giving off of rays of energy or particles by the breaking apart of atoms of certain elements
