Electrons in atoms are arranged in energy levels (n), sublevels (l), and orbitals (ml). Quantum mechanics treats electrons as waves that can only gain or lose discrete amounts of energy called quanta when changing energy levels. Each energy level corresponds to a row on the periodic table and can contain one or more sublevels representing blocks. Sublevels include s, p, d and f orbitals which electrons fill according to specific rules. The electronic configuration notation specifies the distribution of electrons among the atomic orbitals.

1. Answer the following:
Country :
Province :
City :
Street :

2. Arrangement of Electrons in Atoms
Electrons in atoms are arranged as
LEVELS (n)
SUBLEVELS (l)
ORBITALS (ml)

3. Quantum Mechanics
http://www.meta-synthesis.com/webbook/30_timeline/310px-Bohr-atom-PAR.svg.png
 Better than any previous model, quantum
mechanics does explain how the atom behaves.
 Quantum mechanics treats electrons not as
particles, but more as waves (like light waves)
which can gain or lose energy.
 But they can’t gain or lose just any amount of
energy. They gain or lose a “quantum” of
energy.
A quantum is just an amount of energy that the electron
needs to gain (or lose) to move to the next energy level.
In this case it is losing the energy and dropping a level.

4. Energy Levels
http://www.chem4kids.com/files/art/elem_pertable2.gif
 Quantum mechanics has a
principal quantum number. It is
represented by a little n. It
represents the “energy level”
similar to Bohr’s model.
 n=1 describes the first energy
level
 n=2 describes the second energy
level
 Etc.
 Each energy level represents a
period or row on the periodic
table. It’s amazing how all this
stuff just “fits” together.
Red n = 1
Orange n = 2
Yellow n = 3
Green n = 4
Blue n = 5
Indigo n = 6
Violet n = 7

5. Sub-levels = Specific Atomic Orbitals
 Each energy level has 1 or more “sub-
levels” which describe the specific
“atomic orbitals” for that level.
 n = 1 has 1 sub-level (the “s” orbital)
 n = 2 has 2 sub-levels (“s” and “p”)
 n = 3 has 3 sub-levels (“s”, “p” and “d”)
 n = 4 has 4 sub-levels (“s”, “p”, “d” and
“f”)
 There are 4 types of atomic orbitals:
 s, p, d and f
 Each of these sub-levels represent the
blocks on the periodic table.
Blue = s block

6. Orbitals
http://media-2.web.britannica.com/eb-media/54/3254-004-AEC1FB42.gif
http://upload.wikimedia.org/wikipedia/commons/thumb/e/e1/D_orbitals.svg/744px-D_orbitals.svg.png
 In the s block, electrons are going into s orbitals.
 In the p block, the s orbitals are full. New electrons are going into the p orbitals.
 In the d block, the s and p orbitals are full. New electrons are going into the d orbitals.
 What about the f block?
s p
d

7. Table:
s = 2 p = 6 d = 10 f = 14
 Complete the chart in your notes as we discuss this.
 The first level (n=1) has an s orbital. It has only 1.
There are no other orbitals in the first energy level.
 We call this orbital the 1s orbital.
Energy
Level
Sub-
levels
Total Orbitals Total
Electrons
Total Electrons
per Level
n = 1 s 1 (1s orbital) 2 2
n = 2 s
p
1 (2s orbital)
3 (2p orbitals)
2
6
8
n = 3 s
p
d
1 (3s orbital)
3 (3p orbitals)
5 (3d orbitals)
2
6
10
18
n = 4 s
p
d
f
1 (4s orbital)
3 (4p orbitals)
5 (4d orbitals)
7 (4f orbitals)
2
6
10
14
32

8. Electronic Configuration
The electron configuration is
the specific way in which the
atomic orbitals are filled.
It tells where all electrons “live.”

9. Rules for Electronic Configuration
 The Aufbau Principle requires that the electrons occupy the
lowest possible energy level before filling up the next.
 Pauli’s Exclusion Principle posits that no two electrons can
have the same set of four quantum number; the spin quantum
number limits the number of electrons in an orbital to a
maximum of two.
 Hund’s Rule requires that the electrons fill the orbitals in a
subshell one by one, before pairing the electrons in an orbital
spin in opposite directions.

10. Electron Configurations
2p4
Energy Level
Sublevel
Number of electrons in
the sublevel
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6
6s2 4f14… etc.

11. Practice
1. Ne – 10
2. Ca – 20
3. Fe- 26