1. Aim: How is the electron organized in the atom?
D0 Now: Explain the difference between the Bohr Model and the Electron Cloud Model.

2. Electron
Electrons are found in the electron cloud
Negative charge
In a neutral atom the # of protons = the # electrons
The electron cloud has very little mass (low density, large volume); therefore, the atom is considered to be primarily empty space

3. Electron Cloud Model (Wave Mechanical Model)
In the wave-mechanical model (electron cloud model), the electrons are in orbitals, which are defined as the regions of the most probable electron location (ground state)
The ground state is the state of the electron when it is not excited

4. Atomic Orbitals
An atomic orbital is thought of as the region of space in which there is a high probability of finding an electron
The energy levels of electrons are labeled by principal quantum numbers (n) or shells.
Each shell may have several subshells with several orbitals
)1 )2 )3 )4
nucleus

5. Summary of principal energy levels, sublevels, and orbitals

6. Atomic Orbital shapes

7. Orbital notation
Orbital notation- a shell or energy level is indicated by a number, but the shells are subdivided by subshells
sublevel- a division of a shell
Sublevel is divided into orbitals

8. Orbital notation Orbitals can hold a maximum of two electrons
Magnetic attraction holds the electrons together. The opposite magnetic attraction overcomes the charge repulsion of the two electrons in an orbital. s p d

9. Orbital notation
The s sublevel has one orbital
The p sublevel has 3 orbitals
And the d sublevel has 5 orbitals

10. Electron Configuration
Electron configuration is a condensed way of representing the pattern of electrons in an atom.
In the ground state nitrogen has 7 electrons
1s2 2s2 2p3

11. Afbau Principle
Assign electrons in order of energy levels
Cannot put electrons in the 2s until the 1s is full.

12. Afbau Principle

13. Pauli Exclusion Principle
An atomic orbital can only hold two electrons at a time

14. Hund’s Rule
In filling orbitals having equal energy, electrons are added to the orbitals to half fill them all before pairing occurs
Fill electrons first with same spin (arrow pointing up)