Period Three

Question 1

What is the trend for atomic radius accross period three?

Answer 1

Atomic radius increases accross period three, there are more protons yet similar shells and shielding. So the attraction between the nucleus and outer electrons is stronger

Question 2

What is the trend for forst ionisation energy accross period three?

Answer 2

First ionisation energy increases, more protons but similar shells and shielding sonthe attractuon between the nucleus and electron being lost is stronger

Question 3

What happens when sodium reacts with water?

Answer 3

It fizzes ciolently, melts imto a ball and dissolves

Question 4

What halpens when magnesium reacts with cold water?

Answer 4

Very slow reaction, bubbles form

Question 5

What happens when magneisum reacts with steam?

Answer 5

Bright white light ,a white solid powder of magnesium oxide

Question 6

What elements from period three do not react with water?

Answer 6

Aluminium, silicon, sulfur and argon

Question 7

Why does aluminium not react with water?

Answer 7

It is coated in AlO3

Question 8

What happens when chlorine reacts with water? What type of reaction is this?

Answer 8

A pale green colution forms, and it turns litmus paper red and then white
Its a disproportionate reaction, because chlorine is oxidised to HClO and reduced to HCl

Question 9

What is a disproportionate reaction?

Answer 9

Where an element is blth oxidised and reduced

Question 10

What can be seen when sodium, magnesium and aluminium reacts with oxygen?

Answer 10

Sodium- yellow flame, white solid of NaO2 forms
Magnesium- bright white light, white powder of MgO forms
Aluminium - slow reaction, a white solid of Al2O3 dorms

Question 11

What happens when silicon reacts with oxygen?

Answer 11

Very slow reaction to form SiO2

Question 12

What are the two different reactions of phosphorus and oxygen? What different observations can be seen?

Answer 12

P4 + 5O2 —> P4O10 (white flames)
4P + 5O2 —> P4O10 (white fumes)

Question 13

What happens when sulfur reacts with oxygen?

Answer 13

Blue flame, produces SO2 (choking gas)

Question 14

What happens when sulfur dioxide continues to react with oxugen?

Answer 14

SO3 is formed

Question 15

Between metal oxides and non-metal oxides, whoch is acidic and which is basic?

Answer 15

Metal oxides are acidic, non-metal oxides are basic

Question 16

How do metal oxides react with water?

Answer 16

They react with water to produce metal hydroxides. As the oxide ions react with water to form hydroxide ions.

Question 17

Describe the solubility and pH of metal hydroxides

Answer 17

pH decreases accross the period
Solubility decreases, NaOH is very soluble, Mg(OH)2 is sparingly soluble, and aluminium oxide does not react to form a hydroxide so is insoluble.

Question 18

Hpw do non-metal oxides react with water?

Answer 18

They react woth water to produce solutions containing H+ ions, with low pH

Question 19

What happens when silicon oxide reacts woth water?

Answer 19

It is insoluble

Question 20

What is the product and pH when phosphorus oxide reacts with water?

Answer 20

It produces H3PO4, pH 1

Question 21

What is the product and pH when SO3 reacts woth water?

Answer 21

Produces H2SO4, pH 1

Question 22

What is the product and pH when SO2 reacts with water? What reaction forms?

Answer 22

Produces H2SO3, pH 3
Forms a reversible reaction, where equilibrium lies to the left

Question 23

Are period three ionic oxides basic or acidic?

Answer 23

Basic

Question 24

Are period three covalent oxides basic or acidic?

Answer 24

Acidic

Question 25

What does amphoteric mean?

Answer 25

A species that can act as an acid or a base.

Question 26

Give an example lf an amphoteric oxide

Answer 26

Aluminium oxide

Question 27

Give examples lf reactions that show aluminium oxode is amphoteric

Answer 27

Reactions with acids
• Al2O3 + 6HNO3 —> 2Al(NO3) + 3H2O
• Al2O3 + 3H2SO4 —> Al2(SO4)3 + 3H2O

Reaction with bases
• Al2O3 + 2NaOH +H2O —> NaAl(OH)4

Question 28

What happens when aluminium salts are dissolved in water?

Answer 28

An acidic solution is formed.
The lattice breaks down and the aluminium ions become surrounded by six water molecules.
Each molecule bonded with co-ordinate bonds. This forms a hexaaqua ion.

The charge in the Al ions causes the electron density in the water molecules to move closer to the Al ion. So the water molecules become polarised.

This breaks an O-H bond in one of the water molecules, whoch donates a H+ ion.
This creates a reversible reaction

Question 29

What happens when a strong base is added to a hexaaqua ion?

Answer 29

Produces an insoluble precipitate of aluminium hydroxide Al(H2O)3(OH)3 and water.

Question 30

Name an amphoteric hydroxide

Answer 30

Aluminium hydroxide

Question 31

Aluminium hydroxide is amphoteric, when does it act as an acid? Give equations and observations

Answer 31

When reacted with a base, and excess sodium hydroxide is used
Al(OH)3(OH)3 + OH- —> [Al(OH)2(OH)4 ]- + H2O
The white precipitate of aluminium hydroxide dissolves to form a colourless soultion

Question 32

Aluminium hydroxide is amphoteric, when does it act as a base? Give equations and observations

Answer 32

Acts as a base when reacted with an acid

Al(OH)3(OH)3 + 3H+ —> [Al(H2O)6 ]3+
The white precipitate lf aluminium hydroxide dissolves to form a colourless solution.