State and give the formula of the five gases that were found in the early atmosphere.

The answer for #3 is c but i don't know why

Asample of radium-226 will decay 1/4 of its original amount after 3200years. what is the half-life of radium-226?

This flow chart shows the amount of energy that is emitted by each type of light. ultraviolet > blue light > yellow light > red light (maximum energy) (minimum energy) in an experiment, shining which type of light on a strip of metal would be least likely to produce the photoelectric effect? ultraviolet light dim blue light bright red light bright yellow light