Unit 24 the Halogens, Their Uses and Compounds

7/31/2019 Unit 24 the Halogens, Their Uses and Compounds

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Unit 19: The Transitional Metals

Unit 18: Metals and their Properties

Unit 17: The Alkali Metals

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Unit 31: Radioactivity

Unit 30: Light and the Electromagnetic Spectrum

Unit 29: Electricity

Unit 28: Generating Electricity and its Domestic Use

Unit 27: Energy

Unit 26: Rates of Reaction

Unit 25: The Noble Gases, their Properties and Uses

Unit 24: The Halogens, their Uses and Compounds

Unit 23: Ionic and Covalent Compounds

Unit 22: Elements, Molecules and Compounds

Unit 21: Rock Cycle

Unit 20: Crude Oil and its Products


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Unit 24

The Halogens, their Uses and Compounds

Fluorine Bromine

Iodine

9P+

10N

9E-

Chlorine

17P+

18N

17E-

35P+

45N

35E-

53P+

74N

53E-

F

Cl

Br

I

9

17

35

53

19

35

80

127

Fluorine Bromine

Iodine

9P+

10N

9E-

Chlorine

17P+

18N

17E-

35P+

45N

35E-

53P+

74N

53E-

F

Cl

Br

I

9

17

35

53

19

35

80

127


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Unit 24: The Halogens, their Uses and CompoundsUnit 24: The Halogens, their Uses and Compounds Science Interactive LTD Copyright 2005

Understand: Keywords:

1. That group VII elements are called thehalogens.

2. The physical and chemical properties of thegroup VII elements, the halogens.

3. That they have similar chemical and physicalproperties based on their electronicconfiguration.

4. That the halogens can be involved in eitherionic or covalent compounds.

5. Their reactions and compounds with reactivemetals.

6. Their reactions and compounds with nonmetals.

7. That their reactivity increases as you ascendthe group.

8. The uses of the halogens and their compounds.

9. That the halogens and their compounds haveantiseptic properties.

Halogens, Halides, Physical, Chemical,

Properties, Ionic, Covalent, Compounds,

Metals, Non metals, Ions, Bonds, Reactions,

Atoms, Molecules, Reactivity, Monatomic,

Diatomic & Antiseptic.

web: www.science-interactive.co.uk email: [email protected] Interactive LTD PO BOX 50764 LONDON NW6 9AT

Click mouse to begin



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Physical properties of the halogensPhysical properties of the halogens oneone

The halogens have similar chemical properties because

they all have seven electrons in their outer shell. Their

colour darkens as you descend the group from fluorine

a pale yellow gas to iodine a dark purple solid. Their

melting and boiling points also rise as you descend the

group.

The halogens

Notes

Diagram

Found in group VII of the periodic table,

all the halogens have seven electrons in

their outermost electron shell. They are

therefore just one short of a full outer

shell. This is what makes them reactive

with other elements.

Position of the halogens

F9

FluorineFluorine

F9

F9

FluorineFluorine

Cl17

ChlorineChlorine

Cl17

Cl17

ChlorineChlorine

Br35

Br35

I53I

53

Group VII of the periodic table contains a family of very r________ non-metals

known as the halogens. This group contains fluorine, a pale yellow gas, chlorine a

pale green gas, bromine a dark brown liquid and iodine a dark purple solid. They are

not found in their pure state like gold, but are found tied up in c________ or ionic

compounds. They have low melting and boiling points and do not conduct electricity

at all. Give a use for the chloride and fluoride ion ?

The halogens: Word bank: reactive covalent



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Physical properties of the halogensPhysical properties of the halogens twotwo

II

FF

BrBr

ClCl

II

FF

BrBr

ClCl

Br35

Br35

I53I53

Yellow

Green

Brow

n

Purpl

e

F9

FluorineFluorine

F9

F9

FluorineFluorine

Cl17

ChlorineChlorine

Cl17

Cl17

ChlorineChlorine

2,7

2,8,7

F2

Cl2

Br2

I2

2,8,18,7

2,8,18,18,7

The group VII elements, the halogens are all reactive non-metals, able to form both ionic and

covalent compounds with other elements. They have similar physical and chemical properties.

They are all diatomic m_________. As you descend the group their colour deepens from paleyellow to dark purple. Their melting and b__________ points also increase with fluorine and

chlorine being a gas, bromine a liquid and iodine a solid at room temperature. Give a definition

of an ionic and covalent compound ?

Physical properties of group VII halogens:

337oC

59oC

-34oC

-188oC

Boiling point

SolidIodine

LiquidBromine

Electron configurationFormula Colour

Gas

Gas

State at room temperature

Chlorine

Fluorine

Element Symbol

Word bank: molecules boiling



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General antiseptic properties of the halogensGeneral antiseptic properties of the halogensScience Interactive LTD Copyright 2005

II

FF

BrBrClClII

FF

BrBrClCl

Br35

Br35

I53I53

F9

FluorineFluorine

F9

F9

FluorineFluorine

Cl17

ChlorineChlorine

Cl17

Cl17

ChlorineChlorine

The group VII elements, the halogens are well known for their antiseptic properties. Although

they are very toxic to humans at high doses, small quantities of the halogens or their ions (F- Cl-

Br- & I-) have an antiseptic effect, destroying many m_______. Our drinking water is nowchlorinated, making sure that we have clean w______ to drink. Our toothpaste contains fluoride

to help reduce the amount of bacteria in your mouth. Before surgery, iodine water is applied to

our skin to make sure that it is free from microbes.How else can we sterilise surfaces ?

Antiseptic properties of group VII halogens: Word bank: microbes water

All the halogens are potentially harmful substances. Fluorine and chlorine in particular are highly toxic. It is highlydangerous to ingest or breathe halogen vapour or their solutions. They are used to kill bacteria therefore sterilising

water for domestic supply or in swimming pools. Chlorine compounds are used in disinfectants like 'dettol' or 'TCP'.

Iodine water is also used as a disinfectant prior to surgery or to sterilise dirty drinking water.

Bromine IodineChlorineFluorine



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Properties and uses of fluorineProperties and uses of fluorineFluorine is a pale yellow diatomic gas. Two atoms of fluorine form a covalent

molecule, where the atoms share a pair of electrons. Fluorine is the most reactive

halogen. Fluorine is found in a wide range of chemicals including teflon a non stickinert coating for kitchen equipment like s_________. Small amounts of fluoride is

found in toothpaste, to reduce bacteria in our mouths. Fluorine is also used in CFCs, a

refrigerant now banned because of its effects on the o_______ layer. Find out about

other uses of fluorine and its compounds ?

Properties and uses of fluorine:

F9

FluorineFluorine

F9F9

FluorineFluorine

F FF FF FF F

py g

Word bank: saucepans ozone

FluorideDiatomic gas

Fluorine is the most reactive and dangerous of the halogens. It

was used during the first world war to make mustard gas which

when inhaled would destroy your lungs within minutes. Fluorine

forms an extremely stable non-stick compound called teflon.

Developed by NASA scientists, it now coats millions of frying

pans and artificial implants like hip replacement joints.

Non-stick Refrigerants

Fluorine is a pale yellow

diatomic gas. Two atoms of

fluorine covalently bond, sharing

two electrons. The formula offluorine is F2. Fluorine is the

most reactive halogen.

Fluorine



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Properties and uses of chlorineProperties and uses of chlorine

Cl17

ChlorineChlorine

Cl17Cl17

ChlorineChlorine

Cl ClCl ClCl ClCl Cl

BleachDiatomic gas

Chlorine gas is very dangerous if inhaled but in small

amounts it is extremely useful. Since we have chlorinated

our drinking water, our life expectancy has risen

dramatically over the decades. It is also added toswimming pools in higher concentrations to kill bacteria.

Chlorine is also found in salt or sodium chloride (NaCl)

Chlorination Salt

Chlorine is a pale green diatomic

gas. Two atoms of chlorine

covalently bond sharing two

electrons. The formula ofchlorine is Cl2. Chlorine is the

second most reactive halogen.

Chlorine

Chlorine is a pale green diatomic gas. Two atoms of chlorine form a covalent molecule,

where the atoms share a pair of electrons. Chlorine is the second most reactive halogen.

Chlorine is found in a wide range of chemicals including bleach, a disinfectant used toclean surfaces, f______ and toilets. Small amounts of chloride is added to drinking water

to kill any remaining b_________. Chlorine is also found in sodium chloride or table salt

(excessive salt in the diet leads to high blood pressure and cardiovascular problems) Find

out about other uses of chlorine and its compounds ?Properties and uses of chlorine: Word bank: floors bacteria


P i d f b i


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Properties and uses of bromineProperties and uses of bromine

Br35Br35Br Br Br Br Br Br Br Br

Fire extinguishesDiatomic liquid

Bromine is a very toxic brown liquid, but it does have

several uses. Bromine toxicity is used to kill pests that

destroy crops. Bromine is also used in fire extinguishers. It

works by reacting with the oxygen, therefore preventing

further combustion. Bromine is also added to plastics so that

bacteria and moulds do not rot or decompose them.

Pesticides Plastics

Bromine is a brownish diatomic

liquid. Two atoms of bromine

covalently bond, sharing two

electrons. The formula ofbromine is Br2. Bromine is the

third most reactive halogen

Bromine

Bromine is a dark brown diatomic liquid. Two atoms of bromine form a covalent molecule,

where the atoms share a pair of e________. Bromine is the third most reactive halogen.

Bromine is found in a wide range of chemicals including pesticides, which when sprayed oncrops kills pests like locusts. Halon f______ extinguishers contain bromine which extinguishes

small fires that cannot be put out using powder or water. Small amounts of bromine are added

to plastics to prevent their decomposition by bacteria. This is useful for plastics that are used

over long periods of time.Find out about other uses of bromine and its compounds ?

Properties and uses of bromine: Word bank: electrons fire



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Properties and uses of iodineProperties and uses of iodine

I53I53

Iodine is a dark purple diatomic solid. Two atoms of iodine covalently bond sharing two

electrons. Iodine is the l_______ reactive halogen. Iodine is found in high concentrations

in certain seaweeds and in salt water. Iodine is used by the thyroid gland to make theh_________ thyroxin. Humans require small amounts of iodine in their diets. If iodine is

lacking in the diet then goitre, a disease of the thyroid gland can develop. Iodine is also

used to sterilise skin prior to surgical operations. Why dont surgeons use bleach to

sterilise the skin ?Properties and uses of iodine:

I II II II I

Word bank: least hormone

ThyroidDiatomic solid

Iodine is used by the human thyroid gland in order to produce

thyroxine, an essential hormone. If your diet is poor in iodine,

you may develop goitre which is a medical condition where your

thyroid becomes enlarged. Iodine is also used to sterilise your

skin prior to major surgery. It kills the bacteria on your skin.

Explain why halogens, like iodine have an antiseptic effect ?

Goitre Sterilisation

Iodine is a deep purple diatomic

solid. Two atoms of iodine

covalently bond sharing two

electrons. The formula of iodineis I2. Iodine is the least reactive

halogen.

Iodine

R ti f th h lR ti f th h lScience Interactive LTD Copyright 2005


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ClH ClHClH ClHClCl Cl

-

Cl

-

Na

+

Na

+

NaNaNaNaClH ClHClH ClH

ClCl Cl

-

Cl

-

Na

+

Na

+

NaNaNaNa

Sodium chloride Hydrochloric acidSodium + Chlorine Hydrogen + Chlorine

Reactions of the halogensReactions of the halogensThe halogens can either gain electrons to form negative ions during the formation of ionic

compounds or they can form a single covalent bond with other non metals during the formation

of covalent compounds. They do this to become like n______ gases, having a full outer shell.The halogens can react with many metal and non metal elements forming a number of different

ionic and covalent compounds, for example s_________ chloride (NaCl) and carbon tetra

chlorine (CCl4)Draw the electronic configuration of a single atom of fluorine and iodine ?

Formation of ionic and covalent compounds: Word bank: noble sodium

During the formation of the covalent

hydrochloric acid, both atoms form a

single covalent bond. This sharing of

electrons fills the outer shell of bothhydrogen and chlorine atoms making

them both stable.

During the formation of sodium chloride

(NaCl), a single electron from the outer shell of

sodium is transferred to the outer shell of a

single chlorine atom. Both ions (Na+ & Cl-) arenow stable having the same electronic

configuration as a noble gas.

Notes

Diagram

Covalent compoundsIonic compounds


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Covalent halide compoundsCovalent halide compounds


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Halogens also react with themselves and other non-metals to form covalent compounds by

s__________ electrons with the halogens. Carbon tetra chlorine (CCl4) is an important solvent

used in dry cleaning.Draw a dot and cross diagram for C2H4Cl2.

Covalent halide compounds:

Covalent halide compoundsCovalent halide compounds

Cl ClCl Cl

Cl ClCl Cl

C

Cl

Cl

ClCl C

Cl

Cl

ClCl

Cl ClCl ClCC

Cl ClCl Cl

Cl ClCl Cl

C

Cl

Cl

ClCl C

Cl

Cl

ClCl

Cl ClCl ClCC

Carbon + Chlorine

Gro

up

Atom

s

Ionsofatoms

Chlorine + Chlorine

Chlorine molecule (Cl2) Carbon tetra chlorine (CCl4)

x2

Ratio non metal:halogen 1:4Others: F2 Br2 I2 Ratio halogen:halogen 1:1

Word bank: sharing

Displacement of halogens from their compoundsDisplacement of halogens from their compoundsScience Interactive LTD Copyright 2005


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Displacement of halogens from their compoundsDisplacement of halogens from their compoundsThe halogens become less reactive as you descend the group, for example reactions with other

elements involving fluorine and chlorine occur without heating. Reactions with bromine only occur if

heated and reactions involving iodine proceed slowly with strong heating. The reason why fluorine isthe most r_________ halogen is because its the smallest atom and it is the best at capturing or

gaining an electron from other e_________ during reactions. What's the rule for the groupImetals ?

Reactivity of the group VII halogens: Word bank: reactive element

Fluorine

Chlorine

Bromine

Iodine

Br35

Br35

I53I53

F9

FluorineFluorine

F9

F9

FluorineFluorine

Cl17

ChlorineChlorine

Cl17

Cl17

ChlorineChlorine

Displaces

Chlorine

Bromine

Iodine

Displaces

Bromine

Iodine

Displaces

Iodine

Displaces

Nothing

Displace

halide

ionsfrom

theirsolution

Fluorine will displace chlorine, bromine and iodine ions from their solutions like KCl, KBr and KI,

because it is the most reactive halogen.

Fluorine Chlorine Bromine Iodine

+ + + +

_ _ __

Fluorine Chlorine Bromine Iodine

+ + + +

_ _ __

Reactivity of the halogens during reactionsReactivity

mentof

El t l i f b i ( di hl id )El t l i f b i ( di hl id )



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What happens during the electrolysis

Concentrated sodium chloride or brine is

added to the electrolysis cell. This is

heated and allowed to become molten.The current is then switched on and

electrolysis starts.

Electrolysis of sodium chloride

Electrolysis of brine (sodium chloride)Electrolysis of brine (sodium chloride)

Cl17

ChlorineChlorine

Cl17

Cl17

ChlorineChlorine

Chlorine and its compounds are used in huge quantities around the World. Chlorine is

extracted from sodium chloride using e____________. During electrolysis the sodium ion

regains its single electron forming the metal: sodium. Conversely, the chloride ion loses itselectron to form molecular chlorine gas which is then captured at the anode.

Equation: Cathode: 2Na+ + 2e- 2Na Anode: 2Cl- Cl2 + 2e-

Electrolysis of sodium chloride: Word bank: electrolysis

Anode

Cathode

Chlorine gas

NaCl

SodiumMoltenSodium

Molten

Anode

Cathode

Chlorine gas

NaCl

SodiumMoltenSodium

Molten

Chloride (Cl-) ions when molten are

free to move. The chloride ions

being negatively charged travel to

the positive anode. Chloride ions

(Cl-) lose their electron and formdiatomic chlorine (Cl2.) Chlorine is

then used as a gas.

Sodium (Na+) ions when

molten are free to move. The

sodium ions being positively

charged travel to the negative

cathode and regain the electronlost. Molten sodium is formed

at the cathode.

Anode (+ve)Cathode (-ve)


Extension questions and homework


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Extension questions and homework

1: Define the following terms: Halogens, Elements, Reactivity, Gases, Ionic and Covalent.

2: Look at the three pictures below. Complete the table.

3: Answer the following:

a) From physical data, chlorines melting and boiling point is -101oC and -35oC. Between what temperatures

would chlorine be a solid, liquid and gas.

b) All the halogens are diatomic molecules. Explain this term.

c) Name a compound in which a halogen can share an electron in a covalent bond. Do a dot & Cross diagram.

d) Name a compound in which a halogen gain an electron to form an ion. Do a dot & cross diagram.

e) State the type of bonding in the following compounds. Hydrogen fluoride, Lithium chloride, Tetra chloro-

methane, Potassium bromide and Hydrochloric acid.

f) Draw an atom of chlorine from the information given.

Properties and uses

BromineThree

IodineTwo

ChlorineOne

ElementPicture

35.5

Cl

17

4: Complete the following table.Science Interactive LTD Copyright 2005


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p g

5: Answer the following questions:

a) The chemical reactivity of the halogens decreases as you go down the group. Explain why.

b) The boiling and melting points of the halogens increases as you go down the group. Explain why.

6: Complete the following table: Write down the salts formed during the following reactions.

Internet:

Go to google.co.uk and find out the use of fluoride and chloride in drinking water. What form are they used and

when were they first used and what do they aim to prevent.

IIodine

BrownBromine

GasChlorine

7Fluorine

SymbolColourState at room temperatureElectrons in outer shellHalogen

Sodium + Iodine

Magnesium + Chlorine

MgCl2Iron + Bromine

Iron (III) ChlorideIron + Chlorine

FormulaSaltReactants

7: Answer the following questions:

a) How could you determine the pH of bromine liquid, chlorine gas and hydrogen chloride gas.

b) What are silver halide films used for...clue you might have one if you have a suspected broken bone.

c) If you electrolyse sodium chloride solution. (i) What ions would be attracted to the cathode (-ve) (ii) What ions

would be attracted to the anode (+ve) (iii) Why is it impossible to form sodium when electrolysing a solution of

sodium chloride...Explain your answer.

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Unit 24 the Halogens, Their Uses and Compounds

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