1. The Periodic Table and
Identification of Ions and Gases
IGCSE Grade 10 Chemistry

2. What you need to be able to do and
understand:
Group properties Identification of ions and gases
 Describe lithium, sodium and potassium  Use the following tests to identify:
in Group I as a collection of relatively soft Aqueous cations:
metals showing a trend in melting point
and reaction with water.  ammonium, copper(II), iron(II), iron(III)
and zinc by means of aqueous
 Predict the properties of other elements sodium hydroxide and aqueous
in Group I, given data where appropriate. ammonia as appropriate. (Formulae of
 Describe the trends in properties of complex ions are not required.)
chlorine, bromine and iodine in Group VII Anions:
including colour, physical state and
reactions with other halide ions.  carbonate by means of dilute acid and
then limewater,
 Predict the properties of other elements
in Group VII, given data where  chloride by means of aqueous silver
appropriate. nitrate under acidic conditions,
Transition elements  nitrate by reduction with aluminium,
 Describe the transition elements as a  sulfate by means of aqueous barium
collection of metals having high ions under acidic conditions
densities, high melting points and Gases:
forming coloured compounds, and which,
as elements and compounds, often act  ammonia by means of damp red
as catalysts. litmus paper,
Noble gases  carbon dioxide by means of limewater,
 Describe the noble gases as being  chlorine by means of damp litmus
unreactive. paper,
 Describe the uses of the noble gases in  hydrogen by means of a lighted splint,
providing an inert atmosphere, i.e. argon  oxygen by means of a glowing splint
in lamps, helium for filling balloons.

3. Trends of group I the alkali metals
Physical properties:
-good conductors
-very soft (a knife can cut
them)
-low density (they float)
-low melting and boiling
points
Chemical properties:
-all react with H2O but
with increasing reactivity
Metal This metal is silvery and Density (g/cm3) Melts at (°C) Reactivity with water
Li soft 0.53 181 Floats and fizzes
Increasing
Shoots across water reactivity
Na a little softer 0.97 Density 98 Melting
Softness
increases increases point
K softer still 0.86 63 decreases Melts with heat and H2 catches
fire
Rb even softer 1.53 39 Watch the YouTube video.
Cs the softest 1.88 29 Watch the YouTube video.
Make a prediction for Fr (the last in this group)- what are the trends? WHY?

4. Why do we see these trends?
Why do the elements in group I all react in a similar way?
Atoms with the same number of valency electrons react in a similar way.
Why does reactivity increase down group I?
In reactions, the group I atoms lose their outer electron, to gain a stable
outer shell. The more shells there are, the further the outer electron is
from the positive nucleus – so the easier to lose. The easier it is to lose
an electron, the more reactive the metal.
Li
Na
K
How do Rb and Cs
react with water?

5. Trends of group VII the halogens
General information:
-form coloured gases
-are poisonous
-form diatomic molecules
Reactivity DECREASES as
you go down the group.
Halogen At room temperature Boiling point (°C) Reactivity with iron wool
F2 a yellow gas -188 Iron wool burst into flame as fluorine passes
Colour gets Boiling over it – without any heating
deeper and point
Cl2 a green gas -35 Hot iron wool glows brightly decreasing
density increases
increases reactivity
Br2 a red liquid 59 Hot iron wool glows but less brightly
I2 a black solid 184 Hot iron wool shows a faint red glow
Make a prediction for At (the last in this group)- what are the trends? WHY?

6. Why do we see these trends?
Why do the elements in group VII all react in a similar way?
Atoms with the same number of valency electrons react in a similar way.
Why does reactivity decrease down group VII?
Halogen atoms react to gain or share an electron. The positive nucleus of
the atom attracts the extra electron. The more shells there are, the further
the outer shell is from the nucleus. So attracting an electron becomes
more difficult. So reactivity falls.
F
Cl
Br

7. Trends of group o the noble gases
General information:
-unreactive
-form coloured gases
-are non-metals
-are monoatomic
Noble Size and mass of atom Boiling point (°C) A balloon full of this gas
gas
He -269 rises quickly into the air
Ne Increase -246 Boiling
rises slowly
Density
in size point
Ar and mass -186 increases falls slowly increases
Kr -152 falls quickly
Xe -107 falls very quickly
Make a prediction for Rn (the last in this group)- what are the trends? WHY?

8. Why do we see these trends?
Why are the elements in group o unreactive?
Atoms have no need to react in order to gain or lose electrons. They
are already have a stable outer electron shell.
Why does density increase down group o?
The Noble gases grow denser („heavier‟) down the group because the
mass of the atoms increases. The increasing boiling points is a sign of
increasing attraction between atoms. It gets harder to separate them to
form a gas.
He
Ne
Ar

9. What are some uses of noble gases?
Because they are unreactive they are safe to use. When a current is passed
through them they glow.
Gas Uses
Helium -it is lighter than air it is used to fill balloons and airships, it
does not catch fire
Argon -as a filler in light bulbs
-protect metals that are being welded (does not react)
Neon -advertising signs, glows red but colour can be changed if
mixed with other gases
Krypton -lasers (eye surgery)
-car headlights
Xenon -gives a light similar to daylight but with a blue tinge
-car headlights, lighthouse lights, operating rooms
Some
chemistry
fun

10. The transition elements
Physical properties:
-hard, tough and strong
-high melting points
-malleable and ductile
-good conductors of heat
and electricity
-high density
Chemical properties:
-most from coloured
compounds
-they are much less reactive
Some data for some transition metals than group I or II metals
with sodium as a comparison. -most can form ions with
variable charges
Element Density (g/cm3) Melting point (°C) -can form more than one
Fe 7.9 1535 compound with another
Cu 8.9 1083 elements (because of the
variable charge) e.g. FeO
Ni 8.9 1455 and Fe2O3
Na 0.97 98 -from complex ions

11. What are some uses of transition
elements?
 Used in structures such as bridges, building and cars
as alloys– they are strong!
 Many transition elements act as catalysts – e.g.
manganese dioxide (MnO2) in the breakdown of
hydrogen peroxide.
Because you love these chemistry
songs so much! 

12. Testing for ions Cations are positive
Tests for cations Anions are negative
Cation Test Result if positive
ammonium add aqueous
NH4+ sodium hydroxide -ammonia gas produced (red litmus paper turns blue)
(NaOH)
copper(II) -a pale blue precipitate forms
Cu2+ -dissolves on adding more ammonia giving a deep blue
colour
iron(II) add aqueous -a pale green precipitate forms
Fe2+ sodium hydroxide
iron(III) (NaOH) or aqueous
ammonia (NH3) -a red-brown precipitate forms
Fe3+
zinc -a white precipitate forms
Zn2+ -dissolves on adding more NaOH or NH3 giving a
colourless solution
You need to NH4+ Zn2+ Cu2+ Fe2+ Fe3+
know the test
Cu2+ in NH3
but not the (pale blue) and
formulae of Cu2+ in excess
NH3 (dark blue)
complex ions.

13. Testing for ions Cations are positive
Anions are negative
Tests for anions
Anion Test Result if positive
carbonate -add dilute acid (HCl) and then -mixture bubbles and turns limewater
CO32- limewater milky
chloride -add dilute acid (nitric acid) and
-a white precipitate forms
Cl- aqueous silver nitrate
-add sodium hydroxide
nitrate -ammonia gas produced (red litmus
(NaOH), then reduction with
NO3- paper turns blue)
aluminium
sulfate -add dilute acid (HCl) and then
-a white precipitate forms
SO42- aqueous barium nitrate
Cl2+ SO42- NO3- CO32-
You need to know
the test but not the
formulae of
complex ions.

14. Testing for
You need to know the test but not
gases
Tests for gases
the formulae of complex ions.
Gas Test Result if positive
ammonia -damp red litmus
-red litmus paper turns blue
(NH3) paper
carbon dioxide
-add limewater -turns limewater milky
(CO2)
-blue litmus paper turns red
chlorine
-damp litmus paper -universal litmus paper turn red
(Cl2)
-then both are bleached white
hydrogen
-a lighted splint -goes “pop”
(H2)
oxygen
-a glowing splint -splint bursts into flame
(O2)
NH3 CO2 Cl2 O2 H2