Answer:
2h+02=h20
Explanation:
2 in front of h on left side
2 in front of h on right side
They both have two electron shells. Period indicates number of shells.
The answer is long wave length because long wave lengths contians less energy, and would not harm living things such as plants and animals. the more engey a wave length has, the less harmful it is.
short wave length: lots of energy, extremely hot. (examples: gamma rays, and UV (ultraviolet) rays.
long wave lengths: not much energy, safe for humans and other life on Earth.
hopefully this helps.
