Atomic orbitals, electronic configurations and the periodic table

How do electrons behave in an atom?

as standing (stationary) waves

What are standing waves?

Waves that vibrate in time but do not move in space

What are orbitals

Different sizes and shapes of standing waves possible around the nucleus

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

Two

The different shapes of orbitals can be identified as:

s, p, d and f

What is quanta?

The fixed amounts of energy in electrons within atoms

How can you describe any electron in an atom?

Using the four quantum numbers

What does the principal quantum number indicate?

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

What does the angular momentum quantum number determine?

The shape of the subshell and can have values from 0 to n−1

What does the magnetic quantum number determine?

The orientation of the orbital and can have values between -l and +l

What does the spin magnetic number determine?

the direction of spin and can have values of -1/2 or +1/2

Electron within an atom are arranged according to?

• The aufbau principle

• Hund’s rule

• The Pauli exclusion principle

What is the aufbau principle?

Electrons fill orbitals in order of increasing energy

What is Hund’s rule?

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

What is 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 what?

Degenerate

The more stable the electronic configuration, the higher the what?

Ionisation energy

What does VSEPR stand for?

• Valence

• Shell

• Electron

• Pair

• Repulsion

How can the number of electrons an orbital pairs surrounding an orbital be found by:

• taking the total number of valence (outer) electrons on the central atom and adding one for each atom attached

• adding an electron for every negative charge

• removing an electron for every positive charge

• dividing the total number of electrons by two to give the number of electron pairs

Electron pairs are _______ charged and _____ each other

• Negatively

• Repel

How are electrons pair arranged?

To minimise repulsion and maximise separation

The arrangement of electron pairs around a central atom is:

♦ linear for two electron pairs

♦ trigonal planar for three electron pairs

♦ tetrahedral for four electron pairs

♦ trigonal bipyramidal for five electron pairs

♦ octahedral for six electron pairs

Electron pair repulsions decrease in strength in the order:

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