Chemichal Periodicity

Question 1

What is chemical periodicity

Answer 1

Tye regular, repeating pattern of properties obvserved jn the elements in the periodic table . This regular recurrence of properties allows elements to be placed in groups each having similar physical and chemical properties

Question 2

What is group 0 known as

Answer 2

The noble gases are all colourless extremely interactive gases that do not form compounds with other elements as they already have a full outer shell of electrons so are very stable. Monoatomic

Question 3

Why is their variation in properties as groups are descended

Answer 3

The distance of the outer electrons from the pull of the positively charged protons in the nucleus increased down the group as you add an extra shell

Question 4

What happens as you go down the noble gases

Answer 4

Become denser , increase in boiling point

Question 5

Helium

Answer 5

Filling party balloons and airships - helium is much less dense than air
Provides a protective layer by sitting on top of rare documents

Question 6

Neon

Answer 6

Luminiscente lighting

Question 7

Argon

Answer 7

Provides an inert atmosphere e.g in lightbulbs prevents the oxidation of the filament beacuse it won’t react with argon

Question 8

Krypton

Answer 8

In lasers

Question 9

Xeneon

Answer 9

In flash lamps for cameras

Question 10

Why does the boiling point of the noble gases jnrease with the RAM

Answer 10

Beacuse the strength between particles increase as the atom size increases

Question 11

What are the properties of group 1

Answer 11

The alkali metals they have a relatively low density - lithium sodium potassium float on water
Shiny - when freshly cut they rapidly tarnish by reacting with oxygen from ye air .
They are soft - can be easily cut with a shark knife
They have relatively low melting point s- caesium melts in the hand
They are silvery metals except for caesium which is a place hold
They are very reactive - most reactive metal group and are stored under oil or in an argon atmosphere to prevent their reaction with oxygen and moisture in the air

Question 12

What happens as you descend the alkali metals

Answer 12

They become more reactive , softer , more dense

Question 13

Why do the alkali metals change as you descend the group

Answer 13

Because the outer electron shell becomes further from the pull of the protons in the nucleus and therefore becomes easier to remove the metals outer electron and turn the atom into a positive ion so the metals become more reactive , all the number of protons in the nucleus also increases but is compensated for by the effect of the increased number of inner electron shells

Question 14

How do alkali metals react with oxygen

Answer 14

To form oxides e.g 4na +02 = 2(Na20)

Question 15

How do alkali metals react to form hydroxides

Answer 15

2K + 2h20 = 2koh + h2

To form hydroxides and hydrogen

Question 16

How does lithium react with water

Answer 16

Very vigorously , fizzing around on the surface of the water and appearing to dissolve as it forms soluble lithium hydroxide . Doesn’t melt because the reaction is slower so heat isbt produces so quickly and it’s melting point is higher

Question 17

How does sodium react with water

Answer 17

Very vigorously fizzing around rapidly on the surface and appearing to dissolve as it forms soluble sodium hydroxide . With more heat produced and sodiums lower melting point the sodium beacones molten and forms a ball of liquid metal

Question 18

How does potassium react with water

Answer 18

Violently fizzing around very rapidly in a molten ball and appearing to dissolve as it forms soluble potassium hydroxide . Enough heat is produced to ignite the hydrogen gas created by the reaction so a purple flame is seen

Question 19

How can you detect the presence of hydroxide ions

Answer 19

By adding an indicator e.g methyl orange which will turn yellow

Question 20

What are the halogens

Answer 20

Group 7 , reactive non metals that consist of diatomic molecules

Question 21

How should the halogens be used

Answer 21

With caution and in a fume cupboard beacuse of their poisonous vapours

Question 22

What are the properties of fluorine

Answer 22

Pale yellow has very toxic and extremely reactive

Question 23

Chlorine

Answer 23

Pale green gas dense and toxic

Question 24

Bromine

Answer 24

Dense dark red liquid that gives off red brown vapour . Toxic and corrosive

Question 25

Iodine

Answer 25

Dark grey solid , sublimes to give a purple vapour . Forms a brown solution in water and a purple solution in hexane

Question 26

Trends of halogens

Answer 26

On descending the group they become
Less reactive - the further the element is down the group , the further it’s outer shell of electrons is from the nucleus , so the more difficult it becomes to attract an electron to fill the outer shell and form a negative ion
Becomes darker in colour
Increase in melting / boiling point

Question 27

What do the halogens do when heated with the alkali metals

Answer 27

Burn vigorously to form white crystalline halide salts. These are ionic compounds , electrons are transferred from the metal to the non metal forming negatively charged halide ions
2na + cl2 + 2NaCl

Question 28

How can you displace a halogen from its Compound e.g reaction between chlorine and sodium bromide

Answer 28

By using a more reactive halogen , these reactions are done in an aqueous solution
Chlorine + sodium bromide = sodium chloride +bromine colourless. Bromine is oxidised
An orange solution is formed due to the formation of aqueous bromine

Question 29

How do chlorine and sodium iodide react

Answer 29

To form sodium chloride and iodine

Causing a brown solution to form beacuse of aqueous iodine

Question 30

How do you test for iodine

Answer 30

Add a small amount of hexane and shake forming a layer which floats on the aqueous solution and the iodine is absorbed into the hexane layer , forming a purple solution

Question 31

What are the industrial uses of chlorine gas

Answer 31

Used as bleach as sodium chlorite , dissolved in water supply in small amounts to kill bacteria .

Question 32

How do you test for chlorine

Answer 32

Moist Blue litmus is turned white

Question 33

What are halide salts

Answer 33

White salts that dissolve readily in water to form colourless solutions .

Question 34

How can you test for halide ions

Answer 34

Add nitric acid then silver nitrate. Silver ions react with the halide ions to form a precipitate as silver halides are insoluble in water
White - chloride
Cream - bromide
Yellow - iodide

Question 35

What are hydrogen halides

Answer 35

Are colourless gases formed from covalently bonded molecules . When they are dissolved in water , these molecules split up , giving H+ ions and therefore an acidic solution . If dissolved in other solvents the covalent molecules do not split up and no H+ ions are formed and the solution is not acidic.
E.g hcl + h+ and cl-
They are steamy acidic poisonous gases

Question 36

Why do noble gases boiling points increase as you go down the group

Answer 36

Tye attractions between one molecule and it’s neighbour get stronger as the atoms get bigger . More energy is needed to break the stronger intermolecular attractions

Question 37

Properties of halogens

Answer 37

Poor conductors of heat and electricity beacsur they are non metal , when they are solid their crystals will be brittle

Question 38

What is the problem with bromine

Answer 38

Very corrosive

Question 39

How does flourine react with hydrogen

Answer 39

Violent explosion

Question 40

Chlorine and hydrogen

Answer 40

Violent explosion if exposed to a aflame of sunlight

Question 41

Bromine and hydrogen

Answer 41

Mild explosion if exposed to a flame

Question 42

Iodine and hydrogen

Answer 42

Partial reaction to form hydrogen if iodine vapour is heated continuously with hydrogen

Question 43

What happens as you descend the halogen group

Answer 43

As molecules get larger melting and boiling points increase and they become less reactive

Question 44

Explain the trend in reactivity in the halogens

Answer 44

The incoming electron is further away from the nucleus as you go down the group so it is less strongly attracted , this means the ion is less easily formed and the oxidising ability of the halogens falls as you go down the group

Question 45

Transition metals properties

Answer 45

Good conductors of heat and electricity
Workable and strong with high densities
High melting points
Less reactive than group 1 and 2