Inorganic Chemistry: Group 2

Elisa de Toro Arias
Mind Map by Elisa de Toro Arias, updated more than 1 year ago
Elisa de Toro Arias
Created by Elisa de Toro Arias about 4 years ago
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AS - Level A Level – Chemistry Mind Map on Inorganic Chemistry: Group 2, created by Elisa de Toro Arias on 02/07/2016.

Resource summary

Inorganic Chemistry: Group 2
1 TRENDS
1.1 Ionisation Energy
1.1.1 Nuclear charge increases → force of attraction for the e- being removed increases → increase in IE down group
1.1.2 Each added quantum shell → energy of outermost e- increases
1.1.3 Number of filled inner shells increases → force of repulsion on e- being removed increases → decrease in IE down group
1.1.4 Combined effect of the last 2 factors outweighs the effect of 1st factor → decrease in IE down group
1.2 Reactivity
1.2.1 Reactivity of G2 metals increases down group
1.2.2 Atomic radii increases → more shielding → nuclear attraction decreases → easier to remove outer e-
1.3 Melting points
1.3.1 Melting points decrease down the group
1.3.2 Metallic bonding weakens as atomic size increases → distance between cations + delocalised e- increases → electrostatic attractive forces between cations + delocalised e- weaken
1.4 Atomic Radius
1.4.1 Atomic Radius increases down the group
1.4.2 More e- → more shells of e- → bigger atom
2 REACTIONS
2.1 With Oxygen
2.1.1 Group 2 metals burn in oxygen
2.1.2 Magnesium burns with a bright white flame + formation of white solid
2.1.3 GE: 2M(s) + O2(g) → 2MO(s)
2.2 With Chlorine
2.2.1 Group 2 metals combine with chlorine when heated in the gas
2.2.2 GE: M(s) + Cl2(g) → MCl2(s)
2.3 With Water
2.3.1 Magnesium reacts slowly with water + doesn't completely react
2.3.2 Calcium, Strontium & Barium react w increasing vigour → increase in effervescence
2.3.3 GE: M(s) + 2H2O(l) → M(OH)2(aq) + H2(g)
2.3.4 Reaction with Calcium (Calcium Hydroxide is only slightly soluble in water, so liquid turns cloudy: Ca(s) + 2H2O(l) → Ca(OH)2(s) + H2(g)
2.4 Magnesium & Steam
2.4.1 When heated in steam, Magnesium Oxide is formed (white solid) and Hydrogen gas in a vigorous reaction
2.4.1.1 Mg(s) + H2O(g) → MgO(s) + H2(g)
3 REACTIONS OF GROUP 2 OXIDES & HYDROXIDES, & TRENDS IN SOLUBILITY
4 THERMAL STABILITY OF GROUP 2 COMPOUNDS & THE COMPARISON WITH GROUP 1
4.1 Carbonates
4.1.1 G2 carbonates decompose on heating → produce G2 oxides + CO2 gas
4.1.1.1 More thermally stable as you go down the group → bigger cations → less of a polarising effect → distort carbonate ion less → C–O bond is less weakened → doesn't break down easily
4.1.1.2 EXP: Heat known mass of carbonate in boiling tube + pass gas produced through lime water
4.1.1.3 MgCO3(s) → MgO(s) + CO2(g)
4.1.2 G1 carbonates do not decompose apart from Lithium
4.1.2.1 Only have +1 charges → don't have a big enough charge density to polarise the carbonate ion
4.1.2.2 Li → small enough to have polarising effect
4.1.2.3 Li2CO3(s) → Li2O(s) + CO2(g)
4.2 Nitrates
4.2.1 G2 nitrates decompose on heating to produce G2 oxides, O2 gas and NO2 gas
4.2.1.1 Observe brown gas evolving (NO2) + white nitrate solid melt to colourless solution, then resolidify
4.2.1.2 More thermally stable as you down the group → bigger cations → less of a polarising effect → distort carbonate ion less → N–O bond is less weakened → doesn't break down easily
4.2.1.3 Mg(NO3) decomposes the easiest → Mg2+ ion is smallest + has greater charge density → causes more polarisation of nitrate anion → weakens N–O bond
4.2.1.4 2Mg(NO3)2 → 2MgO + 4NO2 +O2
4.2.2 G1 nitrates do not decompose in the same way as G2 (apart from Lithium nitrate) → decompose to give nitrate (III) salt + O2 gas
4.2.2.1 2NaNO3 → 2NaNO2 + O2
5 FLAME TESTS & THE TEST FOR AMMONIUM IONS
5.1 RED: Lithium, Calcium, Rubidium
5.2 YELLOW: Sodium
5.3 LILAC: Potassium
5.4 BLUE: Caesium
5.5 GREEN: Barium
5.6 Heat causes an electron to move to higher energy level → e- is unstable at higher e- level → drop back down → energy is emitted in form of visible light energy → with wavelength of observable light
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