3.2.1 - PERIODICITY

Question 1

Describe and explain the trend of melting points from Na to Al (period 3)

Answer 1

• increases
• charge of the metal cation increases
• attraction between cation and delocalised electrons increase, requiring more energy to break

Question 2

Describe and explain the change in melting point from Aluminium to Silicon (period 3)

Answer 2

• increases
• Si is a giant covalent macromolecule
• infinite lattices, where atoms are held together by strong covalent bonds
• these require large amounts of energy to break

Question 3

Describe and explain how melting points change from phosphorus to argon

Answer 3

• they are simple molecular structures
• change depending on how large the molecule is
• the larger the molecule, the more electrons
• the greater the magnitude of temporary and induced dipoles, increasing the strength of VdW’s

Question 4

State the molecular formula for Phosphorus

Answer 4

P4

Question 5

State the molecular formula for sulfur

Answer 5

S8

Question 6

State the molecular formula for chorine

Answer 6

Cl2

Question 7

State the molecular formula for argon

Answer 7

Ar

Question 8

Describe and explain what happens to atomic radius across a period

Answer 8

• decreases
• nuclear charge increases
• shielding stays the same
• attraction between nucleus and electrons increases, pulling the atom closer together