I- Periodicity

Question 1

Explain the trends for atomic and ionic radius across the period.

Answer 1

• ↓ across the period
• ↑ nuclear charge
• outer e- in same shell- same shielding
• ↑ attraction between nucleus & outer e-
• pulled closer

Question 2

Compare sizes of ions to their equivalent atoms across period 2 (Na–>Cl)

Answer 2

• ionic radius ↓ across period
• Na+, Mg2+, Al3+ –> smaller than their equivalent atoms
  ∵ same no. of e- but ↑ +ve charge ∴ outer e- pulled closer
• Si- x form ions
• P3-, S2-, Cl- –> larger than equivalent atoms

Question 3

Explain the trend of electronegativity across the period

Answer 3

• ↑ nuclear charge (protons in nucleus)
• atomic radius ↓
• ↑ attraction between nucleus & 2 shared e- in covalent bond

Question 4

Explain trend in boiling points across period 2.

Answer 4

Na<Mg<Al
- ↑ nuclear charge
- ↑ delocalised e-
- smaller ions
- ↑ attraction

Si- highest ∵ macromolecular

P4>S8>Cl2

(up x 3 to Si= peak –> big drop–> small rise–> slow drop x 2)

Question 5

Explain trend in melting points from sodium to magnesium

Answer 5

Mg > Na
- ↑ nuclear charge
- ↑ delocalised e-
- ↑ attraction
==> stronger metallic bonds