Lecture Three

Question 1

What was Mendeleev responsible for?

Answer 1

Introduction of the metric system in Russia.
Recognised that the elements should be organised in periods, with vertical groupings corresponding to elements with similar chemical properties.

Question 2

What is an electronic configuration?

Answer 2

The complex arrangement of electrons in an atom.
Electronic configurations are grouped into sub-shells, groups of electrons with the same n and l quantum numbers.
E.g. If n = 2 and l = 1 then electronic configuration is 2p.
E.g. Na electronic configuration is 1s2 2s2 2p6 3s1
Or condensed, it can be written as [Ne] 3s1
Noble gasses are used to condense electronic configurations.

Question 3

Define ground state.

Answer 3

Lowest possible energy state for a set of electrons.

Question 4

Define degenerate.

Answer 4

A set of orbitals with the same amount of energy. E.g. Px, Py and Pz orbitals.

Question 5

Explain Hund’s rule.

Answer 5

States that when filling a degenerate set of orbitals in the ground state, pairing of electrons cannot begin until each orbital in the same set contains one electron. Electrons singly occupying orbitals in a degenerate set have parallel spin.

Question 6

Explain Pauli’s Exclusion Principle.

Answer 6

No two electrons in an atom can have identical four quantum numbers.

Question 7

Explain Aufbau’s Principle.

Answer 7

Involves placing each electron in the lowest possible energy level.