The document explains atomic models, starting with Bohr’s model where electrons exist in fixed energy levels around the nucleus. It introduces the quantum mechanical model, focusing on electron probability and the shapes of atomic orbitals, including s, p, and d orbitals. It also covers electron configuration rules and how quantum theory informs the arrangement of the periodic table.

1. Models of the
Atom

2. Bohr’s model…
• Electrons are found in specific circular
paths (orbits) around the nucleus.
• The electrons have fixed energies called
energy levels. (like rungs on a ladder)
• The amount of energy required to move
an electron to another energy level is
called a quantum.

3. The Quantum Mechanical model
• It is based on the energy and possible
location of an electron.
• how likely it is to find an electron is
described in terms of probability. (ie.
Propeller blades)
• Based on work done by Shrodinger…

5. Atomic Orbitals
• The energy levels of electrons are labeled
by principal quantum numbers (n)
• Each energy sublevel corresponds to an
orbital of a different shape, which describes
where the electron is likely to be found.

6. Atomic Orbitals

7. Shapes and
Orientations of
Orbitals

8. 1s Orbital
• Sphere around the nucleus
The one tells you that the electron
is in the orbital closest to the
nucleus
• S tells you about the shape

9. 2s Orbital
• Similar to 1s except the electron is most
likely in the region farther from the nucleus

10. p Orbitals
• At the first energy level there is only the 1s
orbital, after the second energy level there
are 2p orbitals
• Look like dumbbells
• In the three directions

14. Remember….
MAX NUMBER OF ELECTRONS
IN AN ENERGY LEVEL
ENERGY LEVEL MAX # OF ELECTRONS
1 2
2 8
3 18
4 32
5 50

15. Electron
Configuration
A detailed way of showing the
order in which electrons fill in
around the nucleus

16. Electron Configuration
Symbols
1s2
Energy Level
Sub Level
(s, p, d, f )
# of e-
in
sub level

17. We must follow 3 rules…
• Aufbau priciple
• Electrons occupy energy levels with lowest
energy first.

18. Pauli exclusion principle
• If 2 electrons occupy the same energy level
they must have opposite spins.

19. Hund’s rule…
• Electrons that occupy orbitals of the same
energy will have the maximum number of
electrons with the same spin.
• 2p

20. To start we will use orbital filling
diagrams to help us with electron
configurations….
• Example
Boron- has 5 electrons

21. Periodic table arrangement
• the quantum theory helps to explain the
structure of the periodic table.
• n - 1 indicates that the d subshell in period 4
actually starts at 3 (4 - 1 = 3).
s (n) d (n - 1) p (n)
1
2
3
4
5
6
7
f (n -2)

22. Summary: p orbitals and d orbitals
p orbitals look like
a dumbell with 3
orientations: px,
py, pz (“p sub z”).
Four of the d orbitals resemble two dumbells in a
clover shape. The last d orbital resembles a p
orbital with a donut wrapped around the middle.

23. 1st
Quantum #
Principle Quantum #
(n)
Specifies the energy level
that the electron is on.

24. 2nd
Quantum #
Specifies the shape of the
sub level .
(l)

25. The 3rd
(m) and 4th
quantum
numbers (s) …
• Deals with the orbital within the sublevel
and the spin of the electron.

26. Four Energy Sub-Levels
Energy Level Sub-level Type of sub # of
Orbitals
s Sphere 2 1
p Dumbbell 6 3
d 4-Lobed 10 5
f 6-8 Lobed 14 7