Periodic Table And Such Flashcards
Atomic radius down group 2
Increase
(More shells)
Ionisation energy down group 2
Decrease
(More shells = more distance = less effective nuclear charge = less energy required)
Electronegativity down group 2
Decreases
(More shells = more shielding and more distance = less effective nuclear charge = less electronegative)
GROUP 2
Reactions with water
BERYLLIUM
Reacts with steam at high temps (but basically doesn’t react)
MAGNESIUM
Burns in steam; slight reaction with cold water but forms magnesium hydroxide layer which is insoluble and acts as barrier and also hydrogen
CALCIUM STRONTIUM BARIUM
All react with water with increasing vigour to make (group 2) hydroxide and hydrogen
GROUP 2
Reactions with Oxygen
BERYLLIUM
Burns (when powdered)
ALL OTHERS
Burn to make metal oxide
GROUP 2
Reactions with (dilute) HCl (hydrochloric acid)
All react to form metal chloride and H2 gas
Reactions get more vigorous down the group
GROUP 2
Reactions with (dilute) sulphuric acid
BERYLLIUM AND MAGNESIUM
Similar to HCl; react to form metal sulphate and H2 gas
CALCIUM STRONTIUM BARIUM
Form insoluble/ partially insoluble metal sulphates so layer of insoluble sulphate forms
GROUP 2
Reaction with nitric acid
BERYLLIUM
Can’t tell. Beryllium is Quirky and scientists can’t agree about it
ALL OTHERS
Produce hydrogen gas and metal nitrate
GROUP 2 HYDROXIDES SOLUBILITY
Increase as you go down the group
Larger ionic radius for same ionic charge so charge density decreases so less energy required for lattice dissociation (breaking bonds)
Same hydration enthalpy (forming bonds)
Breaking bonds releases more energy than forming them so more likely to dissolve.
MAGNESIUM: insoluble
CALCIUM: slightly soluble
STRONTIUM AND BARIUM: Soluble
GROUP 2 SULPHATES SOLUBILITY
Decrease down group
Lattice dissociation enthalpy is relatively constant down the group but hydration enthalpy decreases
So less likely to dissolve and form new bonds with water molecules
MAGNESIUM AND CALCIUM: Soluble
STRONTIUM: insoluble
BARIUM: insoluble
GROUP 2 CARBONATES SOLUBILITY
Decreases down group
Basically insoluble
GROUP 2 CARBONATES THERMAL STABILITY
More stable down the group
More shells = less charge dense = less polarising = more stable
Decompose to form group 2 oxide and CO2
GROUP 2 NITRATES THERMAL STABILITY
Thermal stability increases down group
More shells = less charge dense = less polarising = more stable
Decompose to form group 2 oxide and nitrogen dioxide and oxygen
Atomic radius down group 7
Increase
(More shells)
Electronegativity down group 7
Decrease
(Charge density and electron shielding decrease with more shells)
Melting and boiling temperatures down group 7
More electrons as you go down
London forces increase
So harder to separate
So melting point and boiling point increase
Oxidising power down group 7
OIL
F doesn’t lose any
So oxidising power decreases down group
GROUP 7 REACTION WITH HYDROGEN
All make hydrogen halide (HX)
FLUORINE
Explosive explosive
CHLORINE
Explosive exposed to sunlight or flame- makes
BROMINE
Mild explosion in flame
IODINE
Only combine partially even under constant heat (reversible reaction, too)
GROUP 7 REACTION WITH PHOSPHORUS
ALL halogens react with phosphorous to form trihalides (phosphorus (|||) halides)
EXCESS CHLORINE OR BROMINE forms pentahalides (phosphorus (V) halides)
GROUP 7 REACTIONS WITH SODIUM
ALL react to produce sodium halides
GROUP 7 REACTIONS WITH IRON
IRON burns in ALL HALOGEN GASES (except iodine) to give iron (|||) halides
IODINE: only produces iron (||) iodide
GROUP 7 REACTIONS with iron (||) ions
FLUORINE: it’s solution. Won’t work with fluorine, it just reacts with the water
CHLORINE AND BROMINE: oxidise iron (||) to iron (|||) ions. Cl and Br are reduced in the process.
IODINE (in iron (|||)): weak. It is oxidised. (Iron (|||) => Iron (||), and I- => I)
GROUP 7 REACTIONS with SODIUM HYDROXIDE SOLUTION
CHLORINE: DISPROPORTIONATION REACTION
In cold dilute NaOH => bleach (NaCl + NaClO + H2O)
In hot NaOH => sodium chlorate (V) (NaCl + NaClO3 + H2O)
HYDROGEN HALIDES BOILING POINTS
HF high (London and hydrogen bond)
Decrease to HCl (no hydrogen bond)
From HCl to HI (increasing London)
MAKING HYDROGEN HALIDES
Sodium (halide) + sulphuric acid => hydrogen halide + NaHSO4
NaCl + H2SO4 => HCl + NaHSO4
BUT not for iodine; too strong at reducing, so just reduces the sulphur
ACIDITY OF HYDROGEN HALIDES
ALL STRONG ACIDS EXCEPT HF
HF: ionises, but forms an ion pair, so water ions are bound to F- ion
So less effective as an acid
HALIDE IONS AS REDUCING AGENTS
RIL
Less electronegative down the group
Better at losing electrons
So better reducers
TESTING FOR HALIDE IONS
- Nitric acid (to prevent formation of other silver salts)
- Silver nitrate:
F- = no ppt
Cl- = white ppt
Br- = cream ppt
I- = yellow ppt - Ammonia solution (dilute)
AgCl = ppt dissolves
AgBr and AgI = ppt remains - Ammonia solution (concentrate)
AgBr = ppt dissolves
AgI = ppt remains
TESTING FOR SULPHATE IONS
Use BaCl
BaCl reacts with sulphate to make:
- Barium sulphate (white ppt)
- Halogen chloride
TESTING FOR CARBONATE/ HYDROGEN CARBONATES
- React with HCl
- Forms CO2 and metal salt (HCl) and water - Test for CO2 using limewater
- Turns cloudy
TESTING FOR AMMONIUM COMPOUNDS
- Add NaOH
- Ammonia gas is alkaline, so check for it using damp (red) litmus paper
- Turns blue if ammonia gas present
MANUFACTURING CHLORINE
- Put in sodium chloride solution (sodium, chloride, OH- and H+ ions present)
- Cl- and OH- ions gather at anode
- Cl is less electronegative than H so it loses electrons more easily so is discharged from solution
- Two chloride ions each are oxidised and combine to form Cl2 gas - H+ and Na+ ions gather at cathode
- H is more electronegative than Na so it gains electrons more easily so is discharged from solution
- Two H+ ions are each reduced to form H2 gas
- Position of equilibrium shifts and H2O turns into more OH- and H+ ions, leading to congregation of OH- and Na+ ions around cathode: combine to form NaOH
Note: diaphragm used to separate anode and cathode;
- If Cl reacts with H2, explosive mixture created and HCl gas
- If Cl reacts with NaOH, mixture of sodium chloride and sodium chlorate (|) (bleach)
GROUP 1 vs GROUP 2 COMPOUNDS: Thermal stability
Group 1 = lower ionic charge so less polarising so more stable
GROUP 1 CARBONATES: Thermal stability
Thermally stable. Don’t decompose
GROUP 1 NITRATES: Thermal stability
Decompose to form respective nitrite and oxygen
GROUP 1 FLAME TESTS
Lithium: bright red
Sodium: bright yellow
Potassium: lilac
Rubidium: red/ violet
Caesium: blue/ violet
GROUP 2 FLAME TESTS
Beryllium: no colour
Magnesium: no colour
Calcium: brick red
Strontium: bright red
Barium: pale green
