Carbon is not combustible because when it combines with oxygen its energy increases thus it doesnt combust.
Its going to be 2.81 x 1023 atoms
The number of energy levels to which an electron can jump depends on the amount of energy the electron possesses. Each energy level has a specific amount of energy an electron needs to have before it can be in there. So, if an electron doesn't have enough energy to be in that energy level then it won't jump to that higher level.
