Answer:
The same element that contain equal number if protons but different number of neurons in their nuclei and hence differ in relative atomic mass
Gases have high kinetic energy: the molecules are moving much more than in a liquid or solid. You can cut out A and B. In the liquids, the difference is temperature. If a lower temperature is closer to being solid, and a solid has lower kinetic energy than a liquid, then C is the answer. Hope this helps.
The smallest unit that can exist as an element and still have proprieties of that element is an Atom<span />
Where are the substances?
