Groups I & II and the Halogens AS Level Chemistry Edexcel

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Group I, II and the Halogens
Group 1: Alkali Metals
Lithium ­ Li, Sodium ­ Na, Potassium ­ K, Rubidium ­ Rb, Caesium ­ Cs.
Group 2:
Beryllium ­ Be, Magnesium ­ Mg, Calcium ­ Ca, Strontium ­ Sr, Barium ­ Ba.
Metallic Bonding: The electrostatic attraction between the cations and the delocalised
sea of electrons
Melting Point decreases down group because:
Down group, the size of the ion increases.
Therefore the metallic bonding is weaker as the sea of electrons is further away
from the positive protons
Flame test: Dip nichrome wire into HCl and then heat in Bunsen burner. Repeat until no
colour produced
Metal ion Colour
Li+ Red
Na+ Orange
K+ Lilac
Rb+ Red
Cs+ Blue
Be2+ Infra-red
Mg2+ Infra-red
Ca2+ Brick Red
Sr2+ Red
Ba2+ Green
When the electrons are given heat energy by the Bunsen, they jump to a higher energy level.
When the electrons move back down to their energy levels, they emit energy as light, and
their colour depends on the frequency of the light emitted.

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Reaction w/ water:
Group 1 generally happens faster than Group 2.…read more

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Solubility increases down group
Be(OH)2 Mg(OH)2 Ca(OH)2 Sr(OH)2 Ba(OH)2
Solubility decreases down group
Be(OH)2 Mg(OH)2 Ca(OH)2 Sr(OH)2 Ba(OH)2
Only soluble if it is a big molecule with a small molecule
Stability of Carbonates
Group 1 carbonates are all thermally stable in the Bunsen, except for Li2CO3 which acts
as if it were group 2 (because it is such a small ion)
Group 2 carbonates (and Li2CO3) decompose to their Oxides in the Bunsen.
E.g.…read more

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Group 2 decomposes to form the oxide, nitrogen dioxide (brown gas) and oxygen:
2Ca (NO3)2 2CaO + 4NO2 + O2
(Measure the time taken for the brown gas to appear or for a glowing splint to relight)
Group 1 decomposes into nitrite and oxygen (except LiNO3 because other group 1 cations
are not polarising enough to break down the nitrite into NO2)
2NaNO3 2NaNO2 + O2
Halogen Appearance
Fluorine ­ F2 Pale yellow gas
Chlorine ­ Cl2 Green gas
Brown liquid,
Bromine - Br2…read more

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No. of e- shells increase, the shielding increases, and therefore the attraction
NaCl NaBr NaI
NaCl ----- -----
NaBr Yellow/orange colour -----
Brown colour and/or Brown colour and/or
black precipitate black precipitate
c) These affects outweigh the increasing nuclear charge.
Oxidising power: F2>Cl2>Br2>I2
Displacement order: F2>Cl2>Br2>I2
Bromine is extracted from sea water.…read more

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NaBr + H2SO4 NaHSO4 + HCl
H2SO4 + 2H+ + 2e- SO2 + 2H2O
2Br- Br2 + 2e-
H2SO4 + 2Br- + 2H+ SO2 + Br2 + 2H2O
NaI + H2SO4 NaHSO4 + HI
H2SO4 + 2H+ + 2e- SO2 + 2H2O
2I- I2 + 2e-
H2SO4 + 2I- + 2H+ SO2 + I2 + 2H2O
H2SO4 + 6H+ + 6e- S + 4H2O
2I- I2 + 2e-
H2SO4 + 6I- + 6H+ S + 3I2 + 4H2O
H2SO4+ 8H+ + 8e- H2S…read more

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N.b. The HNO3 is to remove any impurities which would react with the AgNO3
Reaction of Cl with NaOH:
At 15C:
o 2NaOH + Cl2 (ox. no. Cl: 0) NaClO (ox. no. Cl: 1) + NaCl (ox. no. Cl: -1) + H2O
o Disproportionation reaction because Cl is oxidised and reduced simultaneously
At 80C:
o 3OCl- (ox. no. Cl: +1) 2Cl- (ox. no. Cl: -1) + ClO3- (ox. no.…read more


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