Arrangement of Electrons in
Atoms
The Quantum Model of the Atom
The Quantum Model of the Atom
Louis De Broglie (1924)
• Suggested that electrons can have a dual waveparticle nature
• Confirmed by experiments which showed electrons
can undergo diffraction and interference
Dr Quantum - Double Slit Experiment - YouTube
The Heisenberg Uncertainty Principle
Werner Heisenberg (1927)
• It is impossible to determine simultaneously the
position and velocity of an electron
• Electrons are detected by interaction with photons
(photons have similar energy to electrons and thus
alter the position of electrons)
Quantum Mechanics: The Uncertainty Principle YouTube
The Schrodinger Wave Equation
Erwin Schrodinger (1926)
• Developed an equation which treated electrons as
waves.
• Solutions to the equation (wave functions) give the
probability of finding an electron in a given location
around the nucleus
Atomic orbital – region of space in which an electron is
most likely to be found
Atomic Orbitals and Quantum Numbers
Quantum Numbers –used to describe the properties of
atomic orbitals and the properties of electrons in
those orbitals
• Three quantum numbers are derived from the
Schrodinger equation and indicate energy level,
orbital shape, and orbital orientation
• One quantum number describes the spin of an
electron in an atomic orbital
Principal Quantum Number
Principal Quantum Number (n)
• Indicates main energy level
occupied by an electron.
• As “n” increases, energy and
distance from the nucleus
increases
Angular Momentum Quantum Number
Angular momentum
quantum number (l)
• Indicates the shape of
the orbital
• Within each energy
level, there are
sublevels.
# sublevels = n
Orbital Letter Designations
and l values
l
Letter
0
s
1
p
2
d
3
f
Shapes of Orbitals
s – orbital
p - orbitals
Shapes of Orbitals
d - orbitals
Shapes of Orbitals
f - orbitals
Magnetic Quantum Number
Magnetic Quantum Number (m)
• Indicates the orientation of the orbital around the
nucleus
Magnetic quantum number
n
l
m
1
0
0
2
0
1
0
-1, 0, +1
3
0
1
2
0
-1, 0, +1
-2, -1, 0, +1, +2
4
0
1
2
3
0
-1, 0, +1
-2, -1, 0, +1, +2
-3, -2, -1, 0, +1, +2, +3
Spin Quantum Number
Spin Quantum Number
• Indicates the spin of an electron in an orbital
Value = + 1/2 or -1/2
• An orbital can hold a maximum of 2 electrons, which
must have opposite spin.
Atomic Orbitals
Orbital Energy Diagram