Periodicity

Question 1

Trend in atomic radius across a period (l to r), why?

Answer 1

Decreases, greater nuclear charge, greater attraction between electrons and nucleus, no extra shielding, outer e-s held more tightly.

Question 2

Trend in melting point (l to r), why?

Answer 2

Varies.
Highest - Si, 4 strong covalent bonds, lots of energy to overcome (think diamond).
Na-Al, electrostatic attraction, increases with ion charge.
P-Ar, VDW increases with size, P4, S8, Cl2, Ar

Question 3

Trend in ionisation energy (l to r), why?

Answer 3

Increases, increased nuclear charge, no extra shielding, greater attraction for the outer e- from the nucleus.

Question 4

On a melting point trend graph what are the rules?

Answer 4

P must be below Na, S must be above Na.