Periodicity UNIT 1

Question 0

Melting and boiling points are linked to….

Answer 0

Bond strength and structure

Question 1

Atomic radius …….. Across a period. Why?

Answer 1

Decreases

As the number of protons increases, the positive charge of the nucleus increases, this means the electrons are pulled closer to the nucleus, making atomic radius smaller
The extra electrons that the elements gain across a period are added to the outer energy level so don’t provide any extra shielding

Question 2

Info on sodium, magnesium and aluminium melting and boiling points

Answer 2

They are metals. Their MP and BP increase across the period as metal-metal bonds get stronger due to the metal ions having more delocalised electrons and a decreasing radius. This leads to a higher charge density which attracts the ions together more strongly

Question 3

Info on silicon MP and BP

Answer 3

It’s Macromolecular, with tetrahedral structure-strong covalent bonds link atoms together. A lot of energy is needed to break these bonds

Question 4

Info on phosphorus, sulphur and chlorine MP and BP

Answer 4

Molecular substances,their MP and BP depend on the strength of the vdw forces between the molecules. Vdw forces weak and easy to overcome - so these elements have low BP and MP

Question 5

Why does sulphur have a higher MP and BP than phosphorus or chlorine

Answer 5

It is a bigger molecule, and the more atoms in a molecule the stronger the vdw forces so higher the MP and BP

Question 6

Info on argon MP and BP

Answer 6

Has very low MP and BP because it exists as individual atoms (monatomic) resulting in very weak vdw forces

Question 7

Ionisation energy generally ………. Across a period. Why?

Answer 7

Increases, because of the increasing attraction between the outer shell electrons and the nucleus, due to the number of protons increasing

Question 8

Which element in period 3 has the highest MP and BP

Answer 8

Silicon

Question 9

Which element in period 3 has the largest atomic radius

Answer 9

Sodium