1. Atomic Spectra
One idea in early 20th century was that an electron (e-) traveled about the nucleus in an orbit. (planetary model)

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

3. Energy Levels
n = 1
n = 2
n = 3
n = 4

4. Relative sizes of the spherical 1s, 2s, and 3s orbitals of hydrogen.

5. p Orbitals
this is a p sublevel with 3 orbitals
These are called x, y, and z
There is a PLANAR NODE thru the nucleus, which is an area of zero probability of finding an electron
3py orbital

6. p Orbitals
The three p orbitals lie 90o apart in space

7. d Orbitals
d sublevel has 5 orbitals

8. The shapes and labels of the five 3d orbitals.

9. f Orbitals
For l = 3, ---> f sublevel with 7 orbitals

10. How many electrons can be in a sublevel?
Remember: A maximum of two electrons can be placed in an orbital.
s sublevel
p sublevel
d sublevel
f sublevel
Number of
orbitals
Number of electrons

12. Electron Configuration
Honors Chemistry
Chapter 4

13. Electron Configuration
The way electrons are arranged around the nucleus.

14. Three rules are used to build the electron configuration:
Aufbau principle
Pauli Exclusion Principle
Hund’s Rule

15. Aufbau Principle
Electrons occupy orbitals of lower energy first.

16. Pauli Exclusion Principle
An orbital can hold only two electrons and they must have opposite spin.

17. Hund’s Rule
In a set of orbitals, the electrons will fill the orbitals in a way that would give the maximum number of parallel spins.
Analogy: Students could fill each seat of a school bus, one person at a time, before doubling up.

18. Aufbau Diagram for Hydrogen

19. Aufbau Diagram for Helium

20. Aufbau Diagram for Lithium

21. Aufbau Diagram for Beryllium

22. Aufbau Diagram for Boron

23. Aufbau Diagram for Carbon

24. Aufbau Diagram for Nitrogen

25. Aufbau Diagram