3.2 - Atomic orbitals, electronic configurations and the Periodic table

Standing wave

This is how electrons behave in an atom. These are waves that vibrate in time but do not move in space

What are orbitals?

different sizes and shapes of standing wave around the nucleus

What is the maximum number of electrons that an orbital can hold?

2

Shapes of orbitals

s, p, d, f

n (principal quantum number)

indicates the main energy level for an electron and is related to the size of the orbital

L (angular momentum quantum number)

determines the shape of the subshell. n-1

Ml (Magnetic quantum number)

determines the orientation of the orbital, can have values between −l to +l

Ms (Spin quantum number)

determines the direction of spin and can have values of -0.5 or +0.5

Aufbau principle

electrons fill orbitals in order of increasing energy

Hund’s rule of Maximum Multiplicity

when degenerate orbitals are available, electrons fill each singly, keeping their spins parallel before spin pairing starts

The Pauli exclusion Principle

no two electrons in one atom can have the same set of four quantum numbers, therefore, no orbital can hold more than two electrons and these two electrons must have opposite spins

In an isolated atom, the orbitals within each subshell are…

degenerate

The variation in first, second and subsequent ionisation energies with increasing atomic number for the first 36 elements can be explained in terms of…

the relative stability of different subshell electronic configurations. This provides evidence for these electronic configurations. Anomalies in the trends of ionisation energies can be explained by considering the electronic configurations

There is a special stability associated with half-filled and full subshells. The more stable the electronic configuration…

the higher the ionisation energy

Electron pairs are negatively charged and repel each other. They are arranged to…

minimise repulsion and maximise separation

2 bonding pairs shape

linear

3 bonding pairs shape

trigonal planar

4 bonding pairs shape

tetrahedral

3 bonding pairs 1 lone pair shape

trigonal pyramidal

2 bonding pairs 2 lone pairs shape

angular

5 bonding pairs shape

trigonal bipyramidal

3 bonding pairs 2 lone pairs shape

trigonal planar

6 bonding pairs shape

octahedral

Electron pair repulsions decrease in strength in the order:

non-bonding pair/non-bonding pair > non-bonding pair/bonding pair > bonding pair/bonding pair