What is the second most common molecule in the body

Can someone me with these questions plz.

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

To apply in a gold the individual gold atoms are united to each other by means of a metallic bond. how would you use the gold block to determine the atomic radius of a gold atom?