IGCSE CHEMISTRY – TOPIC 2
INORGANIC CHEMISTRY
a) GROUP 1 ALKALI METALS (Li, Na and K)
• ALKALI METALS – key names needs are lithium,
sodium and potassium. React vigorously with
water to produce an alkaline metal hydroxide and
hydrogen gas.
• REACTIVITY – reactivity of group 1 metals
INCREASES as you go down the group
• As reactivity increases down group 1, we can
predict rubidium, caesium and francium will react
more vigorously
ELEMENT REACTION WITH WATER WITH AIR
Lithium and water make lithium hydroxide and hydrogen gas
Reaction is slower than sodium, bubbles of hydrogen gas,
LITHIUM (Li) Burns with red flame
melts into a ball, no flame, effeverscence
dissapears at the end of the reaction
Sodium and water make sodium hydroxide and hyrogen gas
Orange/yellow spark, melts into shiny ball, moves around on Burns with yellow/
SODIUM (Na)
surface of water, effervescence, floats (low density), orange flame
dissapears at end of reaction
Potassium and water make potassium hydroxide and hydrogen
gas
POTASSIUM (K) Burns with lilac flame
Lilac flame, melts into ball, dashes around on surface,
bubbles/effervescence - most vigourous reaction
RUBIDIUM (Rb) Explodes with sparks, rubidium hyydroxide produced
Violent explosion due to rapid production of heat and
Caesium (Cs)
hyrdrogen, caesium hydroxide produced
Francium (Fr) Too reactive
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, • ALKALI METALS TREND IN REACTIVITY – increases as you go down –
each outer shell only contains 1 electron – they lose 1 electron to gain
a full outer shell
o As you go further down the number of shells increase, and the
outer electron is further away from the nucleus so there is A
WEAKER ELECTROSTATIC FORCE OF ATTRACTION – this requires
LESS ENERGY to over come making it more reactive as you go
down.
b) GROUP 7 HALOGENS (Cl, Br and I)
• HALOGENS – are group-7 elements. They are all diatomic meaning they
form molecules of two atoms – brittle, crumbly, toxic, poor electric and
thermal conductors, low density
• THE MELTING AND BOILING POINT INCREASES as you go down the
group
HALOGEN STATE COLOUR COLOUR IN SOLUTION
Fluorine Gas Yellow
Chlorine Gas Pale green Green/blue
Red - brown (Evaporates
Bromine Liquid Orange
to brown gas)
Black (sublimes to
Iodine Solid Dark brown
purple gas)
• HALOGENS TRENDS – we can predict things of other halogen:
o Melting and boiling point of halogens increases as you go down so
astatine has the highest, fluorine the lowest
o States become more hard and set as you go down so astatine is a
gas and fluorine is a solid
o Colour becomes darker as you go down so fluorine is the lightest
(yellow) and astatine the darkest (black)
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INORGANIC CHEMISTRY
a) GROUP 1 ALKALI METALS (Li, Na and K)
• ALKALI METALS – key names needs are lithium,
sodium and potassium. React vigorously with
water to produce an alkaline metal hydroxide and
hydrogen gas.
• REACTIVITY – reactivity of group 1 metals
INCREASES as you go down the group
• As reactivity increases down group 1, we can
predict rubidium, caesium and francium will react
more vigorously
ELEMENT REACTION WITH WATER WITH AIR
Lithium and water make lithium hydroxide and hydrogen gas
Reaction is slower than sodium, bubbles of hydrogen gas,
LITHIUM (Li) Burns with red flame
melts into a ball, no flame, effeverscence
dissapears at the end of the reaction
Sodium and water make sodium hydroxide and hyrogen gas
Orange/yellow spark, melts into shiny ball, moves around on Burns with yellow/
SODIUM (Na)
surface of water, effervescence, floats (low density), orange flame
dissapears at end of reaction
Potassium and water make potassium hydroxide and hydrogen
gas
POTASSIUM (K) Burns with lilac flame
Lilac flame, melts into ball, dashes around on surface,
bubbles/effervescence - most vigourous reaction
RUBIDIUM (Rb) Explodes with sparks, rubidium hyydroxide produced
Violent explosion due to rapid production of heat and
Caesium (Cs)
hyrdrogen, caesium hydroxide produced
Francium (Fr) Too reactive
28
, • ALKALI METALS TREND IN REACTIVITY – increases as you go down –
each outer shell only contains 1 electron – they lose 1 electron to gain
a full outer shell
o As you go further down the number of shells increase, and the
outer electron is further away from the nucleus so there is A
WEAKER ELECTROSTATIC FORCE OF ATTRACTION – this requires
LESS ENERGY to over come making it more reactive as you go
down.
b) GROUP 7 HALOGENS (Cl, Br and I)
• HALOGENS – are group-7 elements. They are all diatomic meaning they
form molecules of two atoms – brittle, crumbly, toxic, poor electric and
thermal conductors, low density
• THE MELTING AND BOILING POINT INCREASES as you go down the
group
HALOGEN STATE COLOUR COLOUR IN SOLUTION
Fluorine Gas Yellow
Chlorine Gas Pale green Green/blue
Red - brown (Evaporates
Bromine Liquid Orange
to brown gas)
Black (sublimes to
Iodine Solid Dark brown
purple gas)
• HALOGENS TRENDS – we can predict things of other halogen:
o Melting and boiling point of halogens increases as you go down so
astatine has the highest, fluorine the lowest
o States become more hard and set as you go down so astatine is a
gas and fluorine is a solid
o Colour becomes darker as you go down so fluorine is the lightest
(yellow) and astatine the darkest (black)
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