The document describes the quantum mechanical model of the atom. It states that the model views electrons as existing in clouds or orbitals around the nucleus, with higher probability of finding electrons in regions called principal energy levels or shells. Electrons in inner shells are held more tightly and have lower energy than those in outer shells. Shells are divided into subshells which are further divided into orbitals that can each hold two electrons. Electrons fill the lowest energy orbitals first according to the Aufbau principle.

2. ELECTRONIC
STRUCTURE OF
THE ATOM

3. SECOND QUARTER
ENABLING COMPETENCY
Describe how Bohr’s Model of the atom
improved Rutherford’s Atomic Model.
00

4. QUANTUM MECHANICAL MODEL – views
electron as a cloud of negative charge.
Orbital – region in space
where electrons are most
likely to be found.

5. Specifically, the Quantum Mechanical Model
states the following:
1. Electrons that surround the nucleus are confined to
regions called principal energy levels or shells.
Principal Energy Level or Shell –
region of space around a nucleus
containing electrons having
approximately the same energy.

6. Specifically, the Quantum Mechanical Model
states the following:
1.1 Shells are numbered,
n = 1,23,4,5,6,7 or named as
K, L, M, N, O, P, Q

7. Specifically, the Quantum Mechanical Model
states the following:
1.2 Electrons closer to the
nucleus are held tightly and
are lower in energy.
1.3 Electrons farther from the
nucleus are held less tightly
and are higher in energy.

8. Specifically, the Quantum Mechanical Model
states the following:
1.4 It takes an energy to
move an electron away from
the nucleus to an outer circle.

9. Specifically, the Quantum Mechanical Model
states the following:
1.5 The farther the shell from
the nucleus, the more
electron is can hold.

10. Specifically, the Quantum Mechanical Model
states the following:
AUFBAU PRINCIPLE
- electrons fill atomic orbitals of the
lowest energy levels before
occupying higher levels.

11. Specifically, the Quantum Mechanical Model
states the following:
2. Shells are divided into subshells or sublevels, identified
as s, p, d, f.
Sublevel or subshell – region of
space within an electron shell that
contains electrons that have the
same energy.

12. Specifically, the Quantum Mechanical Model
states the following:
3. The number of
sublevels/subshells in
each principal energy
level or shell is equal to
the number of that
energy level.

13. Specifically, the Quantum Mechanical Model
states the following:
4. These subshells consist of orbitals.
Orbital – region of space
where the probability of finding
an electron is high.

14. Specifically, the Quantum Mechanical Model
states the following:
4.1 Each subshell contains a specific number of orbital.
4.2 Each orbital can hold two electrons

15. Specifically, the Quantum Mechanical Model
states the following:
4.1 Each subshell contains a specific number of orbital.
4.2 Each orbital can hold two electrons
Shell/Energy
Level
Sublevels/
Subshells
Number of Electrons
1 s 2
2 s,p 2 + 6 = 8
3 s,p,d 2 + 6 + 10 = 18
4 s,p,d,f 2 + 6 + 10 + 14 =32
5 s,p,d,f 32