2.1 Periodicity

Question 1

Where are the s orbitals on the periodic table?

Answer 1

First 2 groups

Question 2

Where are the d orbitals in the periodic table?

Answer 2

The ‘middle block’

Question 3

Where are the p orbitals in the periodic table?

Answer 3

Groups 3-8

Question 4

Where are the f orbitals in the periodic table?

Answer 4

The lanthanides

Question 5

What is the atomic radius trend across period 3?

Answer 5

• Decreases
• Charge increases but shielding stays the same.
• Greater attraction so pulls the outer electrons closer to the nucleus.
• Therefore a smaller radius

Question 6

What is the trend if first ionisation energy across period 3?

Answer 6

• Increases

- Stronger nuclear attraction (smaller AR), so needs more energy to lose the outer electrons.

Question 7

What are the exceptions to the 1st IE trend?

Answer 7

• Between gr2 & 3

- Between gr 5 & 6

Question 8

Explain the gr 2 & 3 exception in terms of 1st IE

Answer 8

The outer electron moves from the 2p - 2s orbital, so more shielding from sub shell, and therefore IE decreases here.

Question 9

Explain the gr 5 & 6 exception in terms of 1st IE

Answer 9

Electrons start pairing up in orbitals (Hunds rule), so this ‘pair’ repulsion decreases the IE here.

Question 10

What is the trend in melting points across period 3?

Answer 10

• Na, Mg, Al are metallic so high MP, gets bigger going along these.
• Si is macromolecular, so strong covalent bonds and higher MP than metals.
• P, S, Cl are simple molecular, so weak VDWS. Lower MP than metals but get bigger as you go along these.
• Ar is monatomic so has a very low MP.