1. Periodicity

Question 1

What is periodicity?

Answer 1

The term used to describe repeating patterns in the properties of elements in the periodic table

Question 2

What determines the properties of elements?

Answer 2

Electronic structure

Question 3

What is the position of any element in the periodic table determined by?

Answer 3

Proton number

Question 4

What does it mean, if an element is in the s block?

Answer 4

Their highest energy electrons are in the s block

Question 5

What is a definition of the atomic radius?

Answer 5

The distance between the centre of the nucleus of an atom to its outer most electrons

Question 6

Why is atomic radius measured in a bonded pair of atoms?

Answer 6

As there is no clear end to an electron cloud

Question 7

What is the atomic radii specifically measured using?

Answer 7

A bonded pair of atoms, and therefore half the distance between the centres of a pair of atoms

Question 8

What happens to the atomic radius of atoms across period 3?

Answer 8

It decreases

Question 9

Why does the atomic radii of elements across period three decrease?

Answer 9

• proton number ↑ so nuclear charge ↑
• shielding is constant
• so attraction between outer electrons and nucleus ↑

Question 10

What happens to forces in a substance when it melts?

Answer 10

Some of the ‘forces’ are broken or loosened

Question 11

What happens to forces in a substance when it boils?

Answer 11

All of the ‘forces’ are broken

Question 12

What factors increase melting/boiling points in ionic compounds?

Answer 12

• higher charge → stronger electrostatic forces of attraction
• smaller ions → stronger attraction as can sit more closely to other ions

Question 13

What factors increase melting/boiling points in metallic compounds?

Answer 13

Higher charge on ion → more delocalised electrons → stronger attraction

Question 14

What factors increase melting/boiling points in simple molecular compounds?

Answer 14

• larger molecule → increase van der waal’s forces

* bigger difference in electronegativity

Question 15

What factors increase melting/boiling points in giant covalent compounds?

Answer 15

• more/all covalent bonds → harder to break

graphite - IMFs between layers, diamond - all covalent

Question 16

How is the pattern of melting/boiling points across period 3 elements?

Answer 16

Irregular

Question 17

How can the trend in period 3 melting/boiling points be explained?

Answer 17

The structure of each element is different

Question 18

Why does the melting and boiling point increase from sodium to aluminium, when looking at period 3 elements?

Answer 18

• Na forms 1+ ion; Al forms 3+ ion
• stronger electrostatic forces between electrons and ions in Al
• so Al has a higher m.p. and b.p.

Question 19

Why does silicon have the highest melting point in period three?

Answer 19

• silicon is macromolecular
• so it has many covalent bonds and no IMFs
• and therefore takes more energy to break its bonds

Question 20

Why does silicon have a higher melting point than aluminium but a lower boiling point, when looking at period 3 elements?

Answer 20

• when silicon is melted most covalent bonds are already broken
• so there are not very many bonds left to break when boiling
• whereas Al has a lot of bonds left to break

Question 21

Why is the boiling point from phosphorous to argon lower than from sodium to silicon, when looking at period 3 elements?

Answer 21

• P and Ar - P has IMFs and so does Ar
• Na has metallic bonds and Si is macromolecular - no IMFs
• IMFs are easier to break

Question 22

Why, when looking at period 3 elements, does the boiling point generally decrease from phosphorous to chlorine?

Answer 22

• Cl is a smaller molecule (Cl₂)
• P₄
• weaker VDWs between Cl₂ as there are fewer contact forces due to smaller SA

Question 23

Why, when looking at period 3 elements, does sulphur have a higher boiling point than phosphrous?

Answer 23

• S₈
• P₄
• weaker VDWs between P₄ as it is a smaller molecule → fewer contact forces due to smaller SA

Question 24

Why does Argon have the lowest boiling point in period 3?

Answer 24

• it is a noble gas so unreactive

* VDWs only → little energy required to break

Question 25

What is the first ionisation energy?

Answer 25

The energy to remove 1 mole of electrons from 1 mole of gaseous atoms

Question 26

What happens to ionisation energy across period 3?

Answer 26

General increase

Question 27

Why is there an increase in ionisation energy across period 3?

Answer 27

• proton number ↑
• shielding constant so atomic radius ↓
• attraction between outer electrons and the nucleus ↑