Answer:
Radium is used to produce Radon
Explanation:
Radon is a gas used to treat cancer (certain types).
Answer: Calcium
Explanation:
not 100% sure but i looked it up and got calcium. 99% sure.
Answer: Electrons
Explanation:The electron itself is small but it takes space as much as an atom by circling around the nucleus.
Hepta is seven and tetra is four, so option c is your answer