1. Modern Structure of Hydrogen atom

2. Subshells in the energy levels
Orbitals: Three dimensional region of space where the electrons reside. They have various shapes. n = 1 s n = 2 s p n = 3 s p d n = 4 s p d f

4. Electron Configuration
Chemistry

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

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

7. Electron Configurations
The electron configuration of an atom is a shorthand method of writing the location of electrons by sublevel.
The sublevel is written followed by a superscript with the number of electrons in the sublevel.
If the 2p sublevel contains 2 electrons, it is written 2p2

8. Aufbau Diagram for Hydrogen

9. Aufbau Diagram for Helium

10. Electron Configuration
Na: 1s2 2s2 2p6 3s1

11. Electron Configuration
Na: 1s2 2s2 2p6 3s1
Ne: 1s2 2s2 2p6

12. Electron Configuration
Na: 1s2 2s2 2p6 3s1
Ne: 1s2 2s2 2p6
Na: [Ne] 3s1

13. Blocks and Sublevels
We can use the periodic table to predict which sublevel is being filled by a particular element.