Chemical Periodicity

Question 1

Explain the term mass number

Answer 1

The number of protons and neutrons in the nucleus of an atom.

Question 2

Explain the term isotope

Answer 2

Atoms of the same element that have different numbers of neutrons. (same number of protons)

Question 3

In the modern version of the periodic table the elements are arranged in increasing order of…

Answer 3

atomic number

Question 4

Explain what is meant by a group, and what do its members have in common

Answer 4

A column down the periodic table; same number of electrons in the outer shell

Question 5

Explain what is meant by a period and what its members have in common.

Answer 5

Row across the table; same number of electron shells

Question 6

Describe the trend in chemical reactivity down the group one elements and explain the reason for it.

Answer 6

On descending the group the outer shell electron becomes further from the pull of the protons in the nucleus. Therefore become progressively eassier to remove the metal’s outer electron and turn te atom into a positive ion, so the metals become more reactive.

Although the number of protons inthe nucleus increaed, this is compensated for by the ‘sheilding’ efect of the increased number of inner electrons shells.

Question 7

Describe what you would see when chlorine gas is bubbled through aqueous potassium bromide.

Answer 7

The solution would turn orange due to the formation of aqueous bromine.

Question 8

Describe what you would see if magnesium chloride is mixed with silver nitrate solution.

Answer 8

A white precipitate

Question 9

What is the family name of the group 1 elements

Answer 9

The alkali metals

Question 10

When a group 1 metal is reacted with water, a solution is formed. What would the pH of the resulting solution be

Answer 10

14

Question 11

Describe the test for hydrogen.

Answer 11

Squeaky pop test. A lit splint is put into a test tube of hydrogen and a squeaky pop would be heard.

Question 12

The elements become more reactive as we go down the group 1. Give one piece of evidence to justify this statement.

Answer 12

Group 1 metals react by losing one electron. There would be more effervescence down the group and the flame produced by Hydrogen..

Question 13

Explain why the valency of group one metals is always 1.

Answer 13

There is one electron in the outer shell of each element so the valency is 1

Question 14

Predict two physical properties of astatine

Answer 14

A dark solid, not a good conductor. Solid at room temperature.

Question 15

What is the test for chlorine.

Answer 15

Chlorine gas turns damp blue litmus paper red then bleaches it white.

Question 16

Test for chloride in NaCl.

Answer 16

Sodium chloride is dissolved in water then add silver nitrate solution and nitric acid. If there is a white precipitate then chlorine is present.

Question 17

Test for Sodium in NaCl.

Answer 17

Sodium when heated with a Bunsen burner, turns the flame orange.

Question 18

What is the gas produced on heating sodium nitrate and what is the test for it.

Answer 18

Oxygen, relights a glowing splint.

Question 19

What is the gas produced on heating sodium hydrogencarbonate and what is the test for it.

Answer 19

Carbon dioxide which turns limewater cloudy.

Question 20

What is the gas produced on adding lithium to water.

Answer 20

Hydrogen which makes a squeaky pop when a lit splint is put in it.

Question 21

How do you construct an ionic equation

Answer 21

Write out the full chemical equation including state symbols. Rewrite the equation splitting uo all those things that are both aqueous and ionic (acids are split up into H+ ions and a negatively charge ion). Cancel out spectator ions.

Question 22

What are group 1 elements at room temperature

Answer 22

White crystalline solids.

Question 23

What is the trend in reactivity down the halogen group and explain why it happens.

Answer 23

F is the most reactive halogen because it has the strongest electrostatic attraction for an incoming electron. This is because the outer shell of F (which is where the electron is going) is closer to the nucleus than the outer shells of the other halogens.

Question 24

What is the use of Chlorine

Answer 24

Disinfectant in swimming pools, chemical weaponry (antique)

Question 25

Use of Fluorine

Answer 25

It is added to drinking water and tooth paste. It is good for teeth apparently.

Question 26

Use of Iodine

Answer 26

Iodine has similar effects to chlorine but to a milder extent and so is often used as an antiseptic that is safe for humans.

Question 27

Group 0- The noble gases are all colourless. How do their density and boiling point change down the group?

Answer 27

Density increases and boiling point increases.

Question 28

Trends in the halogens going down the group.

Answer 28

Become less reactive, become darker, increase in melting/boiling point.

Question 29

Colour of aqueous bromine.

Answer 29

Orange

Question 30

Colour of aqueous iodine.

Answer 30

Brown.

Question 31

Test that iodine is present.

Answer 31

Add hexane and shake which forms a purple layer on the aqueous solution.

Question 32

Colour of silver chloride.

Answer 32

White

Question 33

Colour of silver bromide.

Answer 33

Cream

Question 34

Colour of silver iodide.

Answer 34

Yellow

Question 35

Trends upon descending group one?

Answer 35

• Becoems more reactive
• Become softer
• Increase in density

Question 36

What is the use of helium?

Answer 36

• Filling party ballons and airships - helium is less dense than air

Question 37

What is the use of neon?

Answer 37

• Filling gas discharge tubes - to make neon advertising signs

Question 38

What is the use of Argon?

Answer 38

• Provide an inert atmosphere, e.g. lightbulbs to prevent oxidation of the filament, in welding to prevent the metal from burning, in packaging to prevent spoiling of food

Question 39

What is the use of krypton?

Answer 39

• In lasers

Question 40

Use of xenon?

Answer 40

• In flash lamps for cameras

Question 41

What are the properties of fluorine?

Answer 41

• Pale yellow gas
• Very toxic
• Extremely reative

Question 42

What are the properties of chlorine?

Answer 42

• Pale green gas
• Dense
• Toxic

Question 43

What are the properties of bromine?

Answer 43

• Dense
• Dark red liquid
• Gives of red-brown vapour
• Toxic
• Corrosive

Question 44

What are the properties of Iodine?

Answer 44

• Dark grey solid
• Sublimes to give a purple vapour
• Forms a brown solution in water
• Forms purple solution in hexane

Question 45

What happens when halgens are heated with alkali metals?

Answer 45

• Brun vigorously to form white crytalline halide salts.
• These are ionic compounds - elctrons are transferred form metal to the non etal atoms, forming negatively charged halide ions.

Question 46

How can you test the halide ions in sodium chlrodie, sodium bromdie and sodium iodide?

Answer 46

• Place a small smaple of solution in test tuve
• Add few drops of nitric acid
• Then add a few drops of silver nitrate solution

Question 47

What happens when hydrogen halides are dissolved in water?

Answer 47

• The molecules spilt up, giving H⁺ ion and therefore an acidic solution.