Why must an electron absorb a quantum of energy to move to a higher energy level?

For an electron they start at the first level (n=1) I order to move up to the next level (n=2) the amount of quantom energy to move to this next level the energy must be perfect in order to move. If the quantom energy is to small the electron it doesn't try.

precipitation

explanation:

when it goes from cloud to rain/back to earth in the form of rain

nacl or sodium chloride is an ionic compound. this is because an ionic compound pertains to a compound that consists of positively and negatively charged ions. in this case, na (sodium) has a tendency to lose one electron when it reacts with with other atoms, so the resulting sodium ion contains 11 protons and 10 electrons, thus making it positively charged (na+), when chlorine reacts, it usually gains one electron to form an ion called chloride, thus making it negatively charged ( since the ions are oppositely charged, they attract.