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The Quantum Model of the Atom
4.2
Light and Electrons
• Louis de Broglie suggested that e- in
fixed orbitals (like Bohr suggested)
behave with wave like properties.
• He hypothesized that electrons also
have dual particle-wave nature.
Electrons as waves
• Can be diffracted – wave passes by the
edge or through a small opening
• Interference – waves pass over each
other
• Heisenberg uncertainty principle – it is
impossible to determine
simultaneously both the position and
velocity of an e- or any other particle.
Schrödinger
• Schrödinger wave equation –
probability of finding an electron in a
certain orbital
• Schrö and Heis = foundation for …
• Quantum Theory – describes
mathematically the wave properties of
electrons and other very small
particles.
Quantum Numbers
• Orbital – 3-d region around the nucleus
that indicates the probable local of an e• We can learn more than just what orbital
e-s are in…
• Quantum Numbers – specify the
properties of atomic orbitals and the
properties of e- in orbitals
• Like seats at a concert
Principal Quantum Number, n
• PQN–the main E level occupied by the e• n values are positive
• As n increases so does the distance from
the nucleus
• Angular momentum quantum number, l
– the shape of the orbital
• Values can be 0 and any # lower than
what n = (if n=3, l can be 0, 1, and 2)
Magnetic Quantum Number, m
• MQN = the orientation of the orbital
around the nucleus
• Values can be whole numbers, from -l, 0
to +l
• If l = 2, m can be -2, -1, 0, 1, 2
The Spin Quantum Number
• SQN = has only 2 possible values
(+1/2, -1/2) which indicate the two
fundamental spin states of an
electron in an orbital
• A single orbital can hold a max of 2
electrons, but they must have
opposite spin states.