What does it mean for the energy levels in an atom to be quantized? Describe how this affects where electrons can be found

When we describe the energy of a particle as quantized, we mean that only certain values of energy are allowed. ... In this case, whenever we measure the particle's energy, we will find one of those values. If the particle is measured to have 4 Joules of energy, we also know how much energy the particle can gain or lose. Quantized energy means that the electrons can possess only certain discrete energy values; values between those quantized values are not permitted

☆ionisation energy increases across a period from na -> ar☆ionisation energy decreases down a group from li -> fr☆ionic radius decreases across a period from na -> cl☆ionic radius increases down a groupfrom f -> ii hope it clarifies your doubts