L1 - Atoms and Orbitals

Question 1

Hund’s rule:

Answer 1

Degenerate orbitals are filled first.

Question 2

Aufbau Principle:

Answer 2

Electrons enter orbitals of increasing energy.

Question 3

Pauli principle:

Answer 3

2 electrons per orbital.

Question 4

Energy of each level:

Answer 4

S

Question 4

Definition of valency:

Answer 4

Maximum number of univalent atoms that combine to another element under consideration.

Question 5

Examples of Biological molecules:

Answer 5

H C N O P S

Question 6

Definition: Electronegativity

Answer 6

The chemical ability of an atom to attract and electron towards itself. Determines bond type.

Question 7

Electron transfer and formation of bond types:

Answer 7

If one atom more electronegative than other then ion bond forms. Electron transferred to more electronegative atom.

If Electronegativity is equal, then it’s a covalent bond. Electrons shared between atoms.

Question 8

What is a molecular orbital:

Answer 8

It is formed when 2 atomic orbitals merge (hybridised). This forms a low energy bonding molecular orbital and high energy anti bonding orbital.

If more electrons in antibonding orbital than bonding orbital then no bond is formed. High energy means unstable.

Question 9

What are non bonding pairs?

Answer 9

They are lone pairs which occupy non-bonding orbitals.

Question 10

What is a conjugated molecule?

Electron delocalisation:

Examples of conjugated molecules:

Answer 10

Alternate single and multiple bonds. So Pi bonds overlap and electron delocalised.
Increase stability and lowers energy of molecule.

Electron delocalisation: electrons are associated to single atom/covalent bond.

Examples: aromaticity shows conjugated ring of unsaturated bonds so more stable.

Question 11

Resonance hybrid:

Answer 11

Net sum of valid resonance structures.
Has several resonance structure.

Electron delocalised through the whole system and increases stability.