Unit 2: Section 1: Periodicity

Question 1

What do elements in the same period have in common

Answer 1

They have same number of electron shells

Question 2

What is the trend with regards to atomic radiuses across a period and explain why

Answer 2

The atomic radius decreases
As the number of protons increases the positive charge increases - this means electrons are pulled closer to the nucleus
The extra electrons are added to the outer energy level so their isn’t any shielding effect

Question 3

What is the trend in melting points across period 3

Answer 3

Increases from sodium to silicon but then decreases from silicon to argon

Question 4

Explain the trend of melting points between sodium, magnesium and aluminium

Answer 4

Increase across the periods because the metal-metal bonds get stronger because of an increasing positive charge, more delocalised electrons and a decreasing radius

Question 5

Describe the structure of silicon

Answer 5

Macromolecular with a terahedral structure
The strong covalent bonds link all its atoms together

Question 6

Explain the meltingn points of phosphorus, sulfur, chlorine and argon

Answer 6

Made of van der Waals forces so they have low melting points
Sulfur is the biggest molecule so it has the highest melting point
Argon is monatomic so it has a low melting point

Question 7

Explain the trend ionisation energy across period 3

Answer 7

General increase from sodium to argon because of increasing attraction between the outer shell electrons and nucleus due to the number of protosn increasing