Final answer:
A quantum of energy is the minimum quantity of energy needed for an electron to transition from its current energy level to a higher one, following the principles of Bohr's model and Planck's constant.
Step-by-step explanation:
A quantum of energy refers to the minimum quantity of energy that can be lost or gained by an atom. This energy quantum is particularly relevant when considering the behavior of electrons in atoms, which exist only in discrete energy levels characterized by principal quantum numbers (n). When an electron moves from its current energy level to a higher one, it requires the absorption of a quantum of energy, a principle central to Bohr's model of the atom.
The energy difference between the levels is quantified, and in accordance with Planck's constant (h = 6.626 × 10-34 J·s), these differences represent the discrete quanta that electrons can absorb or emit. Hence, the correct completion for the sentence is that a quantum of energy is the amount of energy required to move an electron from its present energy level to a higher one.