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

Describe 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
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 melting 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 in first 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 protons increasing

Question 8

Where in the periodic table are the alkaline earth metals

Answer 8

In the s block of the periodic table

Question 9

Explain the trend in the atomic radius when you go down a group on the periodic table

Answer 9

The atomic radius gets larger because extra electron shells are added as you go down the group

Question 10

Explain the trend in first ionisation energy as you go down group 2

Answer 10

Decreases as you go down the group
Each element as you go down group 2 has another electron shell compared to the one above it
This means more shielding and the outer electrons are farther away from the nucleus

Question 11

Explain the trend in melting point in the group 2 elements and what is an anomaly to this trend

Answer 11

Decrease - metal ions get bigger but the number of delocalised electrons doesn’t change
The larger the ionic raidus the further away the electrons are from the nuclei - so it takes less energy to break the bonds meaning the melting point decreases
Magnesium is much lower than the other elements because of the crystal structure