Hund’s Rule
In IB chemistry, electrons fill orbitals of the same energy (subshell) one at a time, when each orbital has one they begin to double up.
Pauli’s Exclusion Principle
The maximum number of electrons in an orbital is 2, which spin in opposite directions
Electron distribution can be represented by orbital diagrams:
Oxygen:
There are exceptions to Hand’s filling pattern in the d-block.
This is what’s expected for Chromium in the d-block:
This is what actually happens:
This is because whenever a sub shell is completely or half filled, it is more stable and has a lower potential energy in IB chemistry.
Successive Ionisation Energies: when removing electrons from an element (from out to in), we can see some disproportionate jumps as some electrons are removed. In IB chemistry, this indicates they are being removed from different main energy levels. Generally, ionisation energy increases from left to right across a period. The attraction on the outer electron from extra protons which are added across a period increases, and so does the ionisation energy. Down a group it ↓
End of this topic!
Drafted by Gina (Chemistry)