2.1 Periodicity

Question 1

What are the 4 block son the periodic table?

Answer 1

1. S
2. P
3. D
4. F

Question 2

What is periodicity?

Answer 2

The study of the trends within the periodic table. Often these trends are linked to elements electronic configurations

Question 3

What is the trend in atomic radius across a period?

Answer 3

It decreases

Question 4

Why does atomic radius decrease across a period?

Answer 4

1. Increased nuclear force for the same number of electron shells
2. So, outer electrons are pulled in closer to the nucleus because the charge produces a greater attraction

Question 5

What is the trend in atomic radius going down a group?

Answer 5

Going down a group, atomic radius increases

Question 6

Why does atomic radius increase going down a group?

Answer 6

1. With each increment going down a group, an electron shell is added
2. This increases the distance between the outer electrons and the nucleus, reducing the power of attraction
3. More shells also increase shielding whereby the inner shells create a barrier that blocks the attractive forces
4. The nuclear attraction is reduced further and atomic radius increases

Question 7

What is the trend in ionisation energy along a period?

Answer 7

Along a period, ionisation energy increases

Question 8

Why does ionisation energy increase along a period?

Answer 8

1. It increases because atomic radius decreases, hence nuclear charge increases
2. This means that the outer electrons are held more strongly so more energy is required to remove the outer electron and ionise the atom

Question 9

What is the trend in ionisation energy going down a goup?

Answer 9

Going down a group I.E decreases

Question 10

Why does ionisation energy decrease going down a group?

Answer 10

The nuclear attraction between the nucleus and outer electrons reduces and shielding also increases. Both of these factors mean less energy is required to remove the outer electrons

Question 11

What does the melting point of period 3 elements depend on?

Answer 11

1. The structure of the element
2. The bond strength

Question 12

Why does the melting point increase dramatically for silicone in period 3?

Answer 12

1. Silicon has a very strong covalent structure
2. So more energy is required to break the strong covalent bonds - giving it a very high melting point

Question 13

Why does the melting point decrease in period 3 between phosphorous and chlorine?

Answer 13

1. Phosphorous, Sulphur and Chlorine are all siple covalent molecules held with weak Van Der Waals forces
2. Less energy is needed to overcome these weak intermolecular forces, so these molecules have relatively low melting points