Conduction, Convection, or Radiation?

Please help!!!

The air that we breath is made mostly of which gaseous molecule

Aphoton is absorbed by an electron that is in the n = 3 state of a hydrogen atom, causing the hydrogen atom to become ionized. very far away from the nucleus, the released electron has a velocity of 750,000 m/s. what was the wavelength of the absorbed photon?

Whithin which type of system is neither the total mass nor the total energy conserved ? a. open b. connected c. isolated d. closed