MARY - Topic 6

Question 1

What happens when using the hydrogenic atomic orbitals as a basis of orbitals in other atoms?

Answer 1

In Hydrogen the 2s and 2p orbitals have the same energy, the 3s,3p and 3d orbitals also have the same energy, because their energies don’t depend on ‘l’ (secondary quantum number).

Question 2

What happens in multi-electron systems?

Answer 2

Orbital energies do depend on ‘l’, so 2s and 2p have different energies.

Question 3

What are the 3 principles which govern the ground state electronic configurations of the elements?

Answer 3

1 = Aufbau principle (electrons enter and fill lower-energy orbitals before filling higher-energy orbitals)

2 = Pauli’s exclusion principle (no two electrons in the same atom can be in the same quantum state, so they can’t have the same set of 4 quantum numbers)

3 = Hund’s Rule of Maximum Multiplicity

Question 4

What is Hund’s Rule of Maximum Multiplicity?

Answer 4

1 = When there are degenerate (equal energy) orbitals available (2px, 2py, 2pz) electrons will enter orbitals singly. Only when all orbitals are half-filled, will pairing-up begin.

2 = This minimises e-e repulsion and maximises the exchange energy of the electronic configuration.

3 = Relative exchange energies (K) can be calculated by considering the number of pairs of parallel sins that exist for electrons of equal energy.

4 = Each pair of electrons can exchange places without changing electronic configuration

5 = The more exchanges that are possible, the more stable the arrangement.

Question 5

When do the largest multiples of ‘K’ arise?

Answer 5

For half or fully filled orbitals (2p3, 2p6) as these have the greatest no. of electron pairs that can exchange places.

Question 6

What is the 1st row of f block called?

Answer 6

Lanthanoids

Question 7

What is the 2nd row of f block called?

Answer 7

Actinoids