The amount of chemical energy is equal to the amount of heat and light energy.
This is due to the principle of conservation of energy, which states that the total energy of a system remains constant.
Sorry for the scribbles lol
D sublevel because the s sublevel has one orbital, the p sublevel has three orbitals, the d sublevel has five orbitals, and the f sublevel has seven orbitals. In the first period, only the 1s sublevel is being filled.