3.2.1 - Periodicity

Question 1

Atomic radius along a period

Answer 1

Decreases due to an increased nuclear charge for the same number of shells. Outer electrons are pulled in closer to the nucleus as the increased charge produces a greater attraction

Question 2

Atomic radius down a group

Answer 2

Increases because the power of attraction is reducing and shielding is increased, nuclear attraction is reduced

Question 3

Ionisation energy along a period

Answer 3

Increases due to decreasing atomic radius and increasing nuclear charge, outer electrons are held more strongly and more energy is required to remove the outer electron

Question 4

Ionisation energy down a group

Answer 4

Decreases due to nuclear attraction reducing and increasing amounts of shielding, less energy is required to remove the outer electron

Question 5

sodium, magnesium and aluminum melting points

Answer 5

increase due to greater positive charged ions, more electrons are released as free electrons so attractive electrostatic forces increase from Na to Al

Question 6

Silicon melting point

Answer 6

very high as it is macromolecular

Question 7

phosphorus, sulphur and chlorine melting points

Answer 7

relatively low and similar as they are simple covalent molecules held with weak van der Waals forces.

Question 8

argon melting point

Answer 8

very low and is a gas at room temp as it is a noble gas existing as individual atoms with a full outer shell. The atom’s very stable and the van der Waals forces are very weak