Question

Model in which electrons are found in fixed levels around the nucleus and require energy to move from level to level:

a. Bohr model
c. Quantum mechanical model
b. Rutherford model
d. Free-electron model

Answer 1

this is Bohr's model of electron shells - this progressed later into the quantum mechanical model which disproved 'shells' but continued to refer to the energy levels as 'shells' for this historic reason

= a. Bohrs model