1. Orbital diagrams

2. Electron configurations allow us to predict which orbital or set of orbitals electrons are likely to occupy.
The properties of elements are often the result of their electron configurations.

3. Orbital diagrams
Orbital diagrams allow us to see even more specifically which orbitals are being occupied and can allow us to predict properties even better.
In orbital diagrams, we not only indicate which set of orbitals are occupied. We indicate how many electrons are in EACH orbital.
To do this, we use lines to represent orbitals and arrows to represent electrons.

4. Orbital diagrams
To properly draw an orbital diagram, we need to follow three simple guidelines.
Aufbau Principle
Pauli Exclusion Principle – two electrons in the same orbital must have opposite spin.
Hund’s Rule – given the choice of multiple orbitals that have the same energy, an electron will go into the empty one before pairing up.

5. Orbital diagrams Example - Draw the orbital diagram for hydrogen.
We know that hydrogen will only use the 1s orbital. Draw a line for that orbital.
To show the one electron in the 1s orbital, draw an “up” arrow.
H: ___ 1s

6. Orbital diagrams Example - Draw the orbital diagram for helium.
We know that helium will only use the 1s orbital.
According to the Pauli Exclusion Principle, two electrons in the same orbital need opposite spins. We show that they have opposite spin by drawing one “up” arrow and one “down” arrow.
He: ___ 1s

7. Orbital diagrams
Continue with the next elements. We now need to use the 2s orbital, as well.
Li: ___ ___
1s 2s
Be: ___ ___

8. Orbital diagrams
Continue with the next elements. These elements use 1s, 2s, and 2p orbitals.
Now, we must use Hund’s rule. All three 2p orbitals have the same energy.
B: ___ ___ ___ ___ ___
1s 2s p
C: ___ ___ ___ ___ ___