What are important features of the quantum mechanical model of atom?

The important features are:
(i) The energy of electrons in atoms is quantized.
(ii) The existence of quantized electronic energy levels is a direct result of the wave like properties of electrons.
(iii) Both the exact position and exact velocity of an electron in an atom can not be determined simultaneously (Heisenberg uncertainty principle).
(iv) An atomic orbital is the wave function ψ for an electron in an atom. Whenever an electron is described by a wave function, we say that the electron occupies that orbital.
(v) The probability of finding an electron at a point within an atom is proportional to [ψ]² at that point. [ψ]² is known as probability density and is always positive.
(vi) From the value of [ψ]² at different points within an atom, it is possible to predict the region around the nucleus where electron will most probably be found.
(vii) In each orbital, the electron has a definite energy. An orbital cannot contain more than two electrons.
(viii) In multi-electron atom, the electrons are filled in various orbitals in order of increasing energy.