3.1 The Periodic Table

Question 1

What did Dobereiner do?

Answer 1

Triads, ordered by atomic weight with similar elements in the middle.

Question 2

What did Newlands do?

Answer 2

Law of octaves, every eighth similar

Question 3

What is the first ionisation energy?

Answer 3

The energy required to remove an electron from one atom in one mole of atoms in the gaseous state.

Question 4

What factors affect first ionisation energy?

Answer 4

Atomic radius, nuclear charge and electron shielding

Question 5

What is ductility?

Answer 5

the ability to be drawn out or stretched.

Question 6

What is another name for group 2 elements?

Answer 6

Alkaline earth metals.

Question 7

Reactivity trend of group 2?

Answer 7

Increases moving down the group.

Question 8

Properties of group 2 metals?

Answer 8

• high melting and boiling points
• light with low densities
• form colourless (white) compounds

Question 9

Reactions between group 2 elements and oxygen?

Answer 9

Vigorous redox reaction to produce ionic oxide.

Question 10

Reactions between group 2 elements and water?

Answer 10

Form hydroxides with the formula M(OH)2 and hydrogen gas.

Question 11

Which group two element does not react with water to form hydroxides and hydrogen?

Answer 11

Beryllium

Question 12

Reactions between group 2 oxides and water?

Answer 12

form metal hydroxides

Question 13

What are group 2 compounds used for?

Answer 13

• neutralising acid soils
• indigestion remedies
• building and construction

Question 14

What is a major drawback of using group 2 carbonates as building materials?

Answer 14

They react readily with acids which leads to erosion due to acid rain

Question 15

Why does reactivity of group 7 elements decrease down the group?

Answer 15

• atomic radius increases

- shielding increases

Question 16

Chlorine colour in water

Answer 16

Pale green

Question 17

Bromine colour in water

Answer 17

Orange

Question 18

Iodine colour in water

Answer 18

Brown

Question 19

Chlorine colour in cyclohexane?

Answer 19

Pale green

Question 20

Bromine colour in cyclohexane?

Answer 20

Orange

Question 21

Iodine colour in cyclohexane?

Answer 21

Violet

Question 22

What is it called when the same element is both reduced and oxidised?

Answer 22

Disproportionation reaction.

Question 23

Define disproportionation reaction.

Answer 23

The oxidation and reduction of the same element in a redox reaction.

Question 24

What is formed when chlorine reacts with water?

Answer 24

Hydrochloric acid and chloric (I) acid

Question 25

How is bleach formed?

Answer 25

When dilute aqueous sodium hydroxide and chlorine react at room temperature - chlorine undergoes a disproportionation reaction

Question 26

How do you identify carbonate ions?

Answer 26

Add a dilute strong acid and collect any gas.

Fizzing and a colourless gas is produced that turns limewater cloudy.

Question 27

How do you test for sulfate ions?

Answer 27

Add dilute HCl and barium chloride and a white precipitate of barium sulfate is produced.
-salt

Question 28

Which order do you carry out tests for unknown substances?

Answer 28

1) carbonate test
2) sulfate test
3) halide test

Question 29

How can you recognise halide ions?

Answer 29

They react with silver ions go form different coloured silver halide precipitates.

Question 30

What colour is silver chloride?

Answer 30

White

Question 31

What colour is silver bromide?

Answer 31

Cream

Question 32

What colour is silver iodide?

Answer 32

Yellow

Question 33

How do you test for halide ions?

Answer 33

Add aqueous solution of silver nitrate, note colour.

Question 34

What do you do if the colour of the silver halide is too hard to distinguish?

Answer 34

Add dilute ammonia and then concentrated ammonia and the note solubility of the precipitate.

Question 35

Which silver halide is soluble in dilute ammonia?

Answer 35

Silver chloride

Question 36

Which silver halide is soluble in only concentrated ammonia?

Answer 36

Silver bromide

Question 37

Which silver halide is insoluble?

Answer 37

Silver iodide.

Question 38

How can you identify ammonium ions?

Answer 38

Add sodium hydroxide and warm. Test gas with red litmus paper. Ammonia will turn red litmus blue.

Question 39

What is periodicity?

Answer 39

A repeating pattern (of properties shown across different periods).

Question 40

Describe how van der waals forces arise.

Answer 40

Uneven distribution of electrons
Creates instantaneous/temporary dipole in molecule
Causes induced dipoles in neighbour molecules

Question 41

Why do simple covalent compounds have low boiling point

Answer 41

Only induced dipoles between molecules

Question 42

What is important when drawing ionisation energy graphs?

Answer 42

Ignore subshells

Question 43

Why does Mg have a higher melting point than Na?

Answer 43

Magnesium ions have a greater charge
Magnesium has more outer delocalised electrons
Magnesium has greater attraction between ions and electrons OR stronger metallic bonding

Question 44

Explain decreasing nuclear radius across period

Answer 44

Protons and nuclear charge increase
Shielding remains the same
Greater pull

Question 45

Do subshells affect shielding?

Answer 45

No

Question 46

Is a barium ion larger or smaller than a barium atom? Explain

Answer 46

Smaller

Less shielding

Question 47

Why does Be have a higher first ionisation energy than B

Answer 47

In B, election being removed is at a higher energy

An s electron is lost in Be AND a p electron is lost in B

Question 48

Why does the reactivity of group 2 decrease down the group?

Answer 48

• increasing atomic radius
• nuclear attraction decreases
• ionisation energy decreases (less energy needed to remove electrons)

Question 49

Why do successive ionisation energies increase with ionisation number?

Answer 49

radius decreases

attraction between remaining neutrons and electrons increases