ighalogenspp.ppt

GROUP VII
The Halogens
A guide for iGCSE students
KNOCKHARDY PUBLISHING
2010
SPECIFICATIONS

GROUP VII
INTRODUCTION
This Powerpoint show is one of several produced to help students
understand selected GCSE Chemistry topics. It is based on the requirements
of the AQA specification but is suitable for other examination boards.
Individual students may use the material at home for revision purposes and
it can also prove useful for classroom teaching with an interactive white
board.
Additional Powerpoints, and the full range of AS and A2 Chemistry topics,
are available from the KNOCKHARDY WEBSITE at...
www.knockhardy.org.uk
All diagrams and animations in this Powerpoint are original and
created by Jonathan Hopton. Permission must be obtained for their
use in any commercial work.

CONTENTS
• Introduction
• Group trends
• Group similarities
• Reaction with metals
• Displacement reactions
• Summary
• Quick quiz
• Hydrogen chloride or hydrochloric acid?
GROUP VII

INTRODUCTION
F
Cl
Br
I
At
THE HALOGENS OCCUR IN GROUP VII OF THE PERIODIC TABLE
Group 1 2 3 4 5 6 7
0

INTRODUCTION
F
Cl
Br
I
At
THE HALOGENS OCCUR IN GROUP VII OF THE PERIODIC TABLE
THEY ARE NON-METALS AND HAVE ELECTRONIC CONFIGURATIONS
JUST ONE ELECTRON SHORT OF THE NEAREST NOBLE GAS
Group 1 2 3 4 5 6 7
0

GROUP PROPERTIES
GENERAL • non-metals
• exist as separate diatomic molecules… eg Cl2
• have seven electrons in their outer shells
• form negative ions with a 1- charge
• reaction with metals and halides

GROUP PROPERTIES
GENERAL • non-metals
• exist as separate diatomic molecules… eg Cl2
• have seven electrons in their outer shells
• form negative ions with a 1- charge
• reaction with metals and halides
TRENDS • appearance
• boiling point
• electronic configuration
• atomic size
• ionic size
• reactivity

GROUP TRENDS
F2
Yellow
Cl2
Green
Br2
Red/brown
I2
Grey
GAS GAS LIQUID SOLID
Colour
State (at RTP)
APPEARANCE
Yellow Green Red/brown Purple
Vapour colour

GROUP TRENDS
INCREASES down Group because more energy is required to separate
the larger molecules.
F2
Yellow
Cl2
Green
Br2
Red/brown
I2
Grey
GAS GAS LIQUID SOLID
Colour
State (at RTP)
APPEARANCE
BOILING POINT
F2
- 188
Cl2
- 34
Br2
58
I2
183
Boiling point / °C
Yellow Green Red/brown Purple
Vapour colour

GROUP TRENDS
• electrons go into shells further from the nucleus
F Cl Br I
2,7 2,8,7 2,8,18,7 2,8,18,18,7
Configuration
ELECTRONIC CONFIGURATION
9 17 35 53
Atomic Number

GROUP TRENDS
F Cl Br I
ATOMIC & IONIC RADIUS
0.064 0.099 0.111 0.128
Atomic radius / nm
NOT TO SCALE

GROUP TRENDS
ATOMIC RADIUS INCREASES down Group
IONIC RADIUS INCREASES down Group
• the greater the atomic number the more electrons there are
these go into shells increasingly further from the nucleus
• ions are larger than atoms - the added electron repels the
others so radius gets larger
F Cl Br I
ATOMIC & IONIC RADIUS
0.064 0.099 0.111 0.128
Atomic radius / nm
F¯ Cl¯ Br¯ I¯
0.136 0.181 0.195 0.216
Ionic radius / nm

GROUP SIMILARITIES
• all the atoms have seven electrons in their outer shell
• ions are larger than atoms - the added electron repels the
others so radius gets larger
ELECTRONIC CONFIGURATION
F Cl Br I
2,7 2,8,7 2,8,18,7 2,8,18,18,7
Configuration
9 17 35 53
Atomic Number

GROUP SIMILARITIES
MOLECULAR FORMULA
F Cl Br I
Covalent Covalent Covalent Covalent
Bonding
F2 Cl2 Br2 I2
Molecular formula
NOT TO SCALE
• all exist as diatomic molecules

GROUP SIMILARITIES
ION FORMATION
F Cl Br I
Configuration
Ion F¯ Cl¯ Br¯ I¯
2,8 2,8,8 2,8,18,8 2,8,18,18,8
• all gain one electron to form a negative ion of charge 1-
• ions are larger than atoms
• the smaller the atom the easier it forms an ion

GROUP SIMILARITIES
ION FORMATION
F Cl Br I
Configuration
Ion F¯ Cl¯ Br¯ I¯
2,8 2,8,8 2,8,18,8 2,8,18,18,8
• all gain one electron to form a negative ion of charge 1-
• ions are larger than atoms
• the smaller the atom the easier it forms an ion
REACTIVITY
F Cl Br I
Reactivity Increasingly reactive
• reactivity decreases down the Group / increases up the Group

REACTIONS OF HALOGENS
1. WITH METALS
2. WITH HALIDES

REACTION OF HALOGENS WITH METALS

HALOGENS REACT WITH METALS TO PRODUCE METAL HALIDES.

THE EASE OF REACTION DECREASES DOWN THE GROUP F > Cl > Br > I

THIS IS BECAUSE ‘THE LARGER THE HALOGEN ATOM, THE LESS
EASILY IT ATTRACTS THE ELECTRON IT NEEDS
TO FILL ITS OUTER SHELL’

THIS IS BECAUSE ‘THE LARGER THE HALOGEN ATOM, THE LESS
EASILY IT ATTRACTS THE ELECTRON IT NEEDS
TO FILL ITS OUTER SHELL’
THE HALIDES OF GROUP I ARE… WHITE IONIC SOLIDS
VERY SOLUBLE IN WATER
SODIUM CHLORIDE (NaCl) IS A TYPICAL GROUP I HALIDE

REACTION WITH ALKALI METALS - Equations
SODIUM CHLORINE SODIUM CHLORIDE
+

Na + Cl2 NaCl

Na + Cl2 NaCl
The equation doesn’t balance - multiply the formulae until it does

2Na + Cl2 2NaCl
Na + Cl2 NaCl
Balanced equation

Cl
SODIUM ATOM
2,8,1
Na
CHLORINE ATOM
2,8,7
11 protons; 11 electrons 17 protons; 17 electrons
SODIUM CHLORIDE FORMATION

Cl
SODIUM ION
2,8
Na
CHLORIDE ION
2,8,8
both species now have ‘full’ outer shells; ie they
have the electronic configuration of a noble gas
+
11 protons; 10 electrons 17 protons; 18 electrons

Cl
SODIUM ION
2,8
Na
CHLORIDE ION
2,8,8
Na Na+ + e¯
2,8,1 2,8
ELECTRON TRANSFERRED
Cl + e¯ Cl¯
2,8,7 2,8,8
+

DISPLACEMENT REACTIONS OF HALOGENS

HALOGENS GET LESS REACTIVE AS THE GROUP IS DESCENDED

THIS DECREASE IN REACTIVITY DOWN THE GROUP CAN BE
DEMONSTRATED USING DISPLACEMENT REACTIONS...
A DISPLACEMENT REACTION IS WHERE ONE SPECIES TAKES THE PLACE
OF ANOTHER IN A COMPOUND.

THIS DECREASE IN REACTIVITY DOWN THE GROUP CAN BE
DEMONSTRATED USING DISPLACEMENT REACTIONS...
A DISPLACEMENT REACTION IS WHERE ONE SPECIES TAKES THE PLACE
OF ANOTHER IN A COMPOUND.
THE REACTIONS ARE EXAMPLES OF REDOX REACTIONS

SODIUM
CHLORIDE
SOLUTION
Colourless
SODIUM
BROMIDE
SOLUTION
Colourless
SODIUM
IODIDE
SOLUTION
Colourless
CHLORINE
WATER
Pale green
BROMINE
WATER
Orange
A SOLUTION OF THE HALOGEN IS ADDED TO A SOLUTION OF A HALIDE
HALIDES ARE SALTS FORMED BETWEEN ELEMENTS AND HALOGENS

SODIUM
BROMIDE
SOLUTION
Colourless
SODIUM
IODIDE
SOLUTION
Colourless
CHLORINE
WATER
Pale green
BROMINE
WATER
Orange
SODIUM
CHLORIDE
SOLUTION
Colourless
NO VISIBLE
REACTION
Experiment 1

SODIUM
CHLORIDE
SOLUTION
Colourless
SODIUM
IODIDE
SOLUTION
Colourless
BROMINE
WATER
Orange
CHLORINE
WATER
Pale green
SODIUM
BROMIDE
SOLUTION
Colourless
BROMINE
produced
Experiment 2

SODIUM
CHLORIDE
SOLUTION
Colourless
SODIUM
BROMIDE
SOLUTION
Colourless
BROMINE
WATER
Orange
CHLORINE
WATER
Pale green
SODIUM
IODIDE
SOLUTION
Colourless
IODINE
produced
Experiment 3

SODIUM
BROMIDE
SOLUTION
Colourless
SODIUM
IODIDE
SOLUTION
Colourless
CHLORINE
WATER
Pale green
BROMINE
WATER
Orange
SODIUM
CHLORIDE
SOLUTION
Colourless
NO VISIBLE
REACTION
Experiment 4

SODIUM
CHLORIDE
SOLUTION
Colourless
SODIUM
IODIDE
SOLUTION
Colourless
CHLORINE
WATER
Pale green
BROMINE
WATER
Orange
SODIUM
BROMIDE
SOLUTION
Colourless
NO VISIBLE
REACTION
Experiment 5

SODIUM
CHLORIDE
SOLUTION
Colourless
SODIUM
BROMIDE
SOLUTION
Colourless
CHLORINE
WATER
Pale green
BROMINE
WATER
Orange
SODIUM
IODIDE
SOLUTION
Colourless
IODINE
produced
Experiment 6

SODIUM CHLORIDE
CHLORINE
SODIUM BROMIDE SODIUM IODIDE
Solution stays
colourless
NO REACTION
Solution goes from
colourless to orange-
yellow
NO REACTION
Solution goes from
yellow
BROMINE FORMED
Solution goes from
yellow
NO REACTION
Solution goes from
colourless to red
IODINE FORMED
BROMINE
Solution goes from
red
IODINE FORMED
SUMMARY OF OBSERVATIONS
1
6
5
2 3
4
The colour change in Experiments 4 and 5 is
due to dilution – there is no reaction

CHLORINE + SODIUM BROMIDE
CHLORINE + SODIUM IODIDE
BROMINE + SODIUM IODIDE
EQUATIONS

CHLORINE + SODIUM BROMIDE BROMINE + SODIUM CHLORIDE
CHLORINE + SODIUM IODIDE IODINE + SODIUM CHLORIDE
BROMINE + SODIUM IODIDE IODINE + SODIUM BROMIDE
EQUATIONS

EQUATIONS
Cl2(aq) + NaBr(aq) —> Br2(aq) + NaCl(aq)
The equation doesn’t balance - multiply the formulae until it does

EQUATIONS
Cl2(aq) + 2NaBr(aq) —> Br2(aq) + 2NaCl(aq)
Cl2(aq) + NaBr(aq) —> Br2(aq) + NaCl(aq)

EQUATIONS
Cl2(aq) + 2Br¯(aq) —> Br2(aq) + 2Cl¯(aq)
Cl2(aq) + 2NaBr(aq) —> Br2(aq) + 2NaCl(aq)
IONIC EQUATION

EQUATIONS
Cl2(aq) + 2I¯(aq) —> I2(aq) + 2Cl¯(aq)
Cl2(aq) + 2NaI(aq) —> I2(aq) + 2NaCl(aq)
IONIC EQUATION

EQUATIONS
Br2(aq) + 2I¯(aq) —> I2(aq) + 2Br¯(aq)
Br2(aq) + 2NaI(aq) —> I2(aq) + 2NaBr(aq)
IONIC EQUATION

THIS SHOWS THAT A MORE REACTIVE HALOGEN WILL DISPLACE
A LESS REACTIVE ONE FROM AN AQUEOUS
SOLUTION OF ITS SALT
SUMMARY

THIS SHOWS THAT A MORE REACTIVE HALOGEN WILL DISPLACE
A LESS REACTIVE ONE FROM AN AQUEOUS
SOLUTION OF ITS SALT
HOWEVER, THIS REACTION DOES NOT TAKE PLACE
BROMINE + SODIUM CHLORIDE CHLORINE + SODIUM BROMIDE
(Bromine is below chlorine in the Group so is less reactive)
EQUATIONS

PRESS THE SPACE BAR TO SEE WHAT HAPPENS
EXPLANATION
17+
CHLORINE ATOM
17 PROTONS
17 ELECTRONS
2,8,7
35+
BROMIDE ION
35 PROTONS
36 ELECTRONS
2,8,18,8
THE CHLORINE ATOM PULLS AN ELECTRON OUT OF THE OUTER SHELL OF
THE BROMIDE ION – THE CHLORINE ATOM BECOMES A CHLORIDE ION AND
THE BROMIDE ION BECOMES A BROMINE ATOM.

BECAUSE BROMINE ATOMS ARE LARGER THAN CHLORINE ATOMS, IT IS
EASIER TO PULL ONE OF THEIR OUTER SHELL ELECTRONS OUT.
CHLORINE NOW HAS THE OUTER SHELL ELECTRONIC CONFIGURATION OF
A NOBLE GAS.
EXPLANATION
CHLORINE ATOM
17 PROTONS
17 ELECTRONS
BROMIDE ION
35 PROTONS
36 ELECTRONS
CHLORIDE ION
17 PROTONS
18 ELECTRONS
BROMINE ATOM
35 PROTONS
35 ELECTRONS

DISPLACEMENT REACTIONS OF HALOGENS - REDOX

A REDOX REACTION INVOLVES BOTH OXIDATION AND REDUCTION

REDUCTION IS THE… GAIN OF ELECTRONS
OXIDATION IS THE… REMOVAL OF ELECTRONS

IN THE REACTION BETWEEN CHLORINE AND SODIUM BROMIDE, CHLORINE
ATOMS PULL ELECTRONS OUT OF BROMIDE IONS.
Cl2(aq) + 2Br¯(aq) ——> Br2(aq) + 2Cl¯(aq)

THE BROMIDE IONS ARE OXIDISED… ELECTRONS ARE REMOVED
OXIDISED
ELECTRONS
REMOVED
CHLORINE IS THE
OXIDISING AGENT

THE CHLORINE ATOMS ARE REDUCED… ELECTRONS ARE GAINED
REDUCED
GAIN OF ELECTRONS
BROMIDE ION IS THE
REDUCING AGENT

THE CHLORINE ATOMS ARE REDUCED… ELECTRONS ARE GAINED
REDUCED OXIDISED
ELECTRONS
REMOVED
GAIN OF ELECTRONS

OXIDISING POWER OF HALOGENS
THIS IS DUE TO THEIR DECREASING OXIDISING ABILITY

F Cl Br I
2,7 2,8,7 2,8,18,7 2,8,18,18,7
Configuration
9 17 35 53
Atomic Number
0.064 0.099 0.111 0.128
Atomic radius / nm
---- DECREASING OXIDISING POWER ----->

F Cl Br I
2,7 2,8,7 2,8,18,7 2,8,18,18,7
Configuration
9 17 35 53
Atomic Number
0.064 0.099 0.111 0.128
Atomic radius / nm
THE SMALLER THE HALOGEN, THE LESS SHIELDING THERE IS AND THE
GREATER THE EFFECTIVE PULL OF THE NUCLEUS.

F Cl Br I
2,7 2,8,7 2,8,18,7 2,8,18,18,7
Configuration
9 17 35 53
Atomic Number
0.064 0.099 0.111 0.128
Atomic radius / nm
THE GREATER THE PULL OF THE NUCLEUS, THE EASIER THE ATOM CAN
PULL AN ELECTRON OUT OF ANOTHER SPECIES.

F Cl Br I
2,7 2,8,7 2,8,18,7 2,8,18,18,7
Configuration
9 17 35 53
Atomic Number
0.064 0.099 0.111 0.128
Atomic radius / nm
THE GREATER THE PULL OF THE NUCLEUS, THE EASIER THE ATOM CAN
PULL AN ELECTRON OUT OF ANOTHER SPECIES.
CONSEQUENTLY, THE BIGGER THE ATOM, THE EASIER AN ELECTRON CAN
BE REMOVED.

SYMBOL
MOLECULAR
FORMULA
APPEARANCE
STATE (room temp)
F
PALE YELLOW
GAS
Cl
FLUORINE IODINE
ELECTRONIC
CONFIGURATION
BOILING POINT
2,7
INCREASES
2,8,7
GAS
ION
(electronic config)
F¯
2,8
Cl¯
2,8,8
REACTION WITH
SODIUM LESS REACTIVE
PRODUCT OF REACTION
WITH SODIUM
SODIUM
FLUORIDE (NaF)
SODIUM
CHLORIDE (NaCl)
PALE GREEN
Br I
BROMINE
CHLORINE
F2 Cl2 Br2 I2
RED-BROWN GREY-BLACK
LIQUID SOLID
2,8,18,7 2,8,18,18,7
Br¯
2,8,18,8
I¯
2,8,18,18,8
SODIUM
BROMIDE (NaBr)
SODIUM IODIDE
(NaI)
GROUP VII - SUMMARY
COLOUR OF VAPOUR PALE YELLOW GREEN RED-BROWN PURPLE

QUICK QUIZ
1. ELEMENTS IN GROUP 7 ARE KNOWN AS THE ………
2. WHAT ARE THE NAMES OF THE ELEMENTS
3. HOW DOES THE ATOMIC NUMBER CHANGE DOWN THE GROUP?
4. HOW DOES THE ELECTRONIC CONFIGURATION CHANGE?
5. HOW DOES THE ATOMIC SIZE (RADIUS) CHANGE?
6. HOW MANY ELECTRONS DO THEY HAVE IN THE OUTER LEVEL?
7. ARE THEY METALS OR NON-METALS?
8. WHAT HAPPENS TO THEIR COLOUR DOWN THE GROUP?
9. DO THEY GO AROUND IN PAIRS OR AS MONATOMIC GASES?
10. WHAT HAPPENS TO THEIR STATE AT ROOM TEMPERATURE?
11. WHAT TYPE OF COMPOUNDS DO THEY FORM WITH METALS?
12. HOW CAN EXPLAIN THEIR RELATIVE REACTIVITY IN TERMS OF THE
ATOMIC STRUCTURE?

QUICK QUIZ - ANSWERS
1. HALOGENS.
2. FLUORINE, CHLORINE, BROMINE, IODINE, ASTATINE.
3. ATOMIC NUMBER INCREASES DOWN THE GROUP.
4. GET MORE SHELLS DOWN THE GROUP.
5. ATOMIC SIZE INCREASES DOWN THE GROUP.
6. THEY ALL HAVE SEVEN ELECTRONS IN THE OUTER LEVEL.
7. THEY ARE NON-METALS.
8. COLOUR DARKENS DOWN THE GROUP.
9. ATOMS GO AROUND IN PAIRS OR AS DIATOMIC GASES.
10. GO FROM GAS TO SOLID DOWN THE GROUP.
11. THEY FORM IONIC COMPOUNDS WITH METALS.
12. THE LARGER THEY ARE THE LESS EASILY ELECTRONS ARE GAINED AND
THE LESS REACTIVE THEY BECOME.

HYDROGEN CHLORIDE OR HYDROCHLORIC ACID?

Hydrogen chloride is a colourless covalent gas; it is a poor conductor of
electricity because there are no free electrons or ions present. It has no
action on dry litmus paper because there are no aqueous hydrogen ions
present.

Hydrogen chloride is a
colourless covalent gas; it is a
poor conductor of electricity
because there are no free
electrons or ions present. It has
no action on dry litmus paper
because there are no aqueous
hydrogen ions present.

Hydrogen chloride is a
colourless covalent gas; it is a
poor conductor of electricity
because there are no free
electrons or ions present. It has
no action on dry litmus paper
because there are no aqueous
hydrogen ions present.
In water, the hydrogen chloride
molecules dissociate into ions. The
solution now conducts electricity
showing ions are present. For each
hydrogen chloride molecule that
dissociates (splits up) one hydrogen ion
and one chloride ion are produced. The
solution turns litmus paper red because
of the H+(aq) ions.

HYDROGEN CHLORIDE HYDROCHLORIC ACID
colourless gas Appearance colourless soln.
covalent molecule Bonding aqueous ions
HCl(g) Formula HCl(aq)
poor Conductivity good
no reaction Dry blue litmus goes red
HCl(g) —> H+ (aq) + Cl¯(aq)

Hydrogen chloride dissociates in water because water is a polar solvent.
However, when hydrogen chloride is placed in an organic solvent such as
methylbenzene it does not dissociate and does not produce H+ ions.
WATER
A polar solvent
Molecules dissociate
The solution turns litmus
paper red because of the
H+(aq) ions.
DOES HYDROGEN CHLORIDE ALWAYS DISSOCIATE?
METHYLBENZENE
A non-polar solvent
NO dissociation
The solution does not
litmus paper red because
there are NO H+(aq) ions.

WATER IS A POLAR SOLVENT –
it has one end which is slightly positive
and another end which is slightly positive.
WHY DOES HYDROGEN CHLORIDE DISSOCIATE IN WATER?
positive
end
negative
end

When a molecule of hydrogen chloride
is put into water, the water molecules
‘encourage’ the covalent bond holding
the hydrogen and chlorine atoms
together to split, thus forming ions.
positive
end
negative
end

The chloride ions are attracted to the
slightly positive hydrogen end of water.
The slightly negative oxygen end of
water attracts the H+ ions.
When a molecule of hydrogen chloride
is put into water, the water molecules
‘encourage’ the covalent bond holding
the hydrogen and chlorine atoms
together to split, thus forming ions.
positive
end
negative
end

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