As an electron in an atom moves from a higher energy state to a lower energy state, the atom 1 becomes a negative ion
2 becomes a positive ion
3 releases energy
4 absorbs energy

3 releases energy

Explanation:

An electron in an energy level has a definite amount of energy associated with it at that level.

Electrons can undergo transitions from one level to another. However, when the electron changes its state, it must absorb or emit the exact amount of energy which will bring it from the initial to the final state.

When the electron is excited, it moves from the ground state to an excited state, it must absorb energy. On returning from an excited state to a lower level or the ground state, energy is emitted, giving rise to a line in the spectrum.

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c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.