each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element.
There are actually two planets referred to as gas giants which are Jupiter and Saturn. These two planets are made of mostly helium and hydrogen which makes them gas giants, while Uranus and Neptune have more ice and rock substances, so they are not considered gas giants.
A. the history is the moths that where white where able to blend in the trees before the pollution of the trees causing the trunks to turn black and the frequency of the blacks being seen to be more then the whites
