1. Electron Energy Level Diagrams

2. The Quantum Atom a dense nucleus composed of protons and neutrons
electrons are arranged around the nucleus.
electrons are arranged in specific energy levels
energy levels are subdivided into smaller divisions called sublevels or subshells
sublevels are divided into orbitals, 3 dimensional spaces where electrons are most likely found.
orbitals are sphere shaped or torus (dumbbell) shaped and can hold a maximum of 2 electrons

3. The Quantum Atom a dense nucleus composed of protons and neutrons
electrons are arranged around the nucleus.
electrons are arranged in specific energy levels
energy levels are subdivided into smaller divisions called sublevels or subshells
sublevels are divided into orbitals, 3 dimensional spaces where electrons are most likely found.
orbitals are sphere shaped or torus (dumbbell) shaped and can hold a maximum of 2 electrons

4. The Quantum Atom a dense nucleus composed of protons and neutrons
electrons are arranged around the nucleus.
electrons are arranged in specific energy levels
energy levels are subdivided into smaller divisions called sublevels or subshells
sublevels are divided into orbitals, 3 dimensional spaces where electrons are most likely found.
orbitals are sphere shaped or torus (dumbbell) shaped and can hold a maximum of 2 electrons

5. The Quantum Atom a dense nucleus composed of protons and neutrons
electrons are arranged around the nucleus.
electrons are arranged in specific energy levels
energy levels are subdivided into smaller divisions called sublevels or subshells
sublevels are divided into orbitals,
3-dimensional spaces where electrons are most likely found.
orbitals are sphere shaped or torus (dumbbell) shaped and can hold a maximum of 2 electrons

6. Random, yet strange science photograph
Neils, next time you make a model of the hydrogen atom, don’t make it to scale!
Blast!
It’s the third one
I‘ve lost this week!
Wolfgang Pauli and Neils Bohr having fun with theoretical physics...

7. Quantum Numbers
Physical chemists use quantum numbers to represent the location of an electron in an atom.
Quantum numbers describe:
which energy level (n),
sublevel,
Orbital,
and direction of spin electrons have.
Each electron has its own unique set of quantum numbers, because no two electrons can be in the exact same place at the exact same time.

8. Maximum number of electrons
Quantum Numbers
Chemists use Electron Energy Level Diagrams to describe the arrangement of electrons around an atom.
These diagrams indicate which orbital energy levels are occupied by electrons for a particular ion or atom.
Energy level Subshells are divided into 4 different types, based on the maximum number of orbitals they can have. Orbitals can hold 2 electrons each.
Sublevel
Number of Orbitals
Maximum number of electrons s 1 2 p 3 6 d 5 10 f 7 14

9. Blocks on the Periodic Table
As it turns out, these sublevels are related to blocks on the periodic table
Sublevel
(aka Block)
Columns of associated elements
Elements found in this “Block” s p d f

10. Blocks on the Periodic Table

11. Example Energy Level Diagram:
Example: Barium Atom
Electrons are placed in these diagrams following these rules:
The aufbau principle:
Electrons always fill lower energy levels before moving to higher energy orbitals.
Hund’s Rule:
Electrons are filled into empty orbitals so that each orbital gets one electron before you start doubling up.
Pauli Exclusion Principle:
No two electrons can be in the same place at the same time. This means that electrons in the same orbital spin in opposite directions and are indicated with arrows in different directions.

12. Example Energy Level Diagram:
Example: Barium Atom
Electrons are placed in these diagrams following these rules:
The aufbau principle:
Electrons always fill lower energy levels before moving to higher energy orbitals.
Hund’s Rule:
Electrons are filled into empty orbitals so that each orbital gets one electron before you start doubling up.
Pauli Exclusion Principle:
No two electrons can be in the same place at the same time. This means that electrons in the same orbital spin in opposite directions and are indicated with arrows in different directions.

13. Example Energy Level Diagram:
Example: Barium Atom
Electrons are placed in these diagrams following these rules:
The aufbau principle:
Electrons always fill lower energy levels before moving to higher energy orbitals.
Hund’s Rule:
Electrons are filled into empty orbitals so that each orbital gets one electron before you start doubling up.
Pauli Exclusion Principle:
No two electrons can be in the same place at the same time. This means that electrons in the same orbital spin in opposite directions and are indicated with arrows in different directions.

14. Example Energy Level Diagram:
Example: Barium Atom
Electrons are placed in these diagrams following these rules:
The aufbau principle:
Electrons always fill lower energy levels before moving to higher energy orbitals.
Hund’s Rule:
Electrons are filled into empty orbitals so that each orbital gets one electron before you start doubling up.
Pauli Exclusion Principle:
No two electrons can be in the same place at the same time. This means that electrons in the same orbital spin in opposite directions and are indicated with arrows in different directions.

15. An “aufbau” mnemonic
This memory aid shows the order of the orbitals as they are filled with electrons:

16. What is an Anion? An ion with a negative charge.
It forms when an atom gains electrons.
The atom gains electrons to fill its valence shell.

17. What is an Cation? An ion with a positive charge.
It forms when an atom loses electrons.
The atom loses electrons to fill its valence shell.