Unformatted text preview: the reference point (nucleus) in 3D
- GIVES shape to orbitals Basic Postulates of Quantum Theory
1. 2. The Quantum Mechanical
Picture of the Atom
3. The allowed energy levels of electrons in an
atom (the energy states) can be described by
sets of numbers called quantum numbers.
• Atoms can exist only in certain energy states. In each
energy state, the atom has a definite energy. When
an atom changes its energy state, it must emit or
absorb just enough energy to bring it to the new
energy state (the quantum condition).
Atoms emit or absorb radiation (light) as they
change their energies. The frequency of the light
emitted or absorbed is related to the energy change
by a simple equation. Quantum Number n
• The principal quantum number ‘n’.
n = 1, 2, 3, 4, ...... “shells”
n = K, L, M, N, ......
The electron’s energy depends mainly on n . Quantum numbers are the solutions of the
Schrödinger & Dirac equations.
Four quantum numbers are necessary to describe
energy states of electrons in atoms. 6 1/21/2014 Quantum Number ℓ Quantum Numbers ml
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