What is thought to happen when electrons jump from a higher level to a lower level

It gains energy and becomes less stable

As the electrons move away from the nucleus, it gains energy and becomes less stable. When electron jumps from lower energy level to higher energy level, it gains energy from surroundings which is known as absorption of energy. When an electron jumps from higher energy level to lower energy level, it releases energy which is known as emission of energy. Note that the electron can absorb or emit only that much amount energy which is equal to energy difference between two levels.