Question

Bohr's model explained electrons can revolve only in certain permitted orbits whose angular could successfully explain stability of atoms and spectrum of unielectron species. Hydrogen spectrum consists of Lyman, Balmer, Paschen, Brackett and Pfund series. Bohr's theory could not explain spectrum of multi-electron species, Stark effect, Zeeman effect, dual nature of matter, de Broglie equation and Heisenberg uncertainty principle which lead to orbital concept. Electrons were filled in orbitals according to Aufbau's principle, Hund's Rule and Pauli's exclusion principle. Each electron is identified by four quantum numbers n, l, ml and ms out which n, l, ml was derived from Schrodinger's wave equation. Half-filled and completely filled orbitals are more stable due to exchange energy and symmetrical distribution of electrons.

Bohr model can explain:

Why is the energy of 1s electron lower than 2s electron?

How orbit is different from orbital?