©HOPTON
Jan 29, 2016
©HOPTON
THE s-BLOCK ELEMENTS
Elements in Group I (alkali metals) and Group II (alkaline earths) are known ass-block elements because their valence (bonding) electrons are in s orbitals.
Could you write down the electron configuration for the first 3 alkali metals and alkaline earth metals?
©HOPTON
THE s-BLOCK ELEMENTS
Elements in Group I (alkali metals) and Group II (alkaline earths) are known ass-block elements because their valence (bonding) electrons are in s orbitals.
Gp I
Li
Na
K
Rb
Cs
Fr
ALKALI METALS
1s2 2s1
… 5s1
… 6s1
1s2 2s2 2p6 3s1
1s2 2s2 2p6 3s23p64s1
©HOPTON
THE s-BLOCK ELEMENTS
Elements in Group I (alkali metals) and Group II (alkaline earths) are known ass-block elements because their valence (bonding) electrons are in s orbitals.
Be
Gp I
Mg
Ca
Sr
Ba
Rn
Li
Na
K
Rb
Cs
Fr
Gp II
ALKALINE EARTHSALKALI METALS
1s2 2s2
… 5s2
… 6s2
1s2 2s2 2p6 3s2
1s2 2s2 2p6 3s23p64s2
1s2 2s1
… 5s1
… 6s1
1s2 2s2 2p6 3s1
1s2 2s2 2p6 3s23p64s1
©HOPTON
THE s-BLOCK ELEMENTS
Elements in Group I (alkali metals) and Group II (alkaline earths) are known ass-block elements because their valence (bonding) electrons are in s orbitals.
Be
Gp I
Mg
Ca
Sr
Ba
Rn
Li
Na
K
Rb
Cs
Fr
Gp II
ALKALINE EARTHSALKALI METALS
1s2 2s2
Francium and radium are both short-lived radioactive elementsFrancium and radium are both
short-lived radioactive elements
… 5s2
… 6s2
1s2 2s2 2p6 3s2
1s2 2s2 2p6 3s23p64s2
1s2 2s1
… 5s1
… 6s1
1s2 2s2 2p6 3s1
1s2 2s2 2p6 3s23p64s1
©HOPTON
GROUP TRENDS
Be
1s2 2s2
Mg
…3s2
Ca
… 4s2
Sr
… 5s2
2,2 2,8,2 2,8,8,2 2,8,18,8,2
New e/c
Old e/c
ELECTRONIC CONFIGURATION
4 12 20 38Atomic Number
Ba
… 6s2
2,8,18,18,8,2
56
©HOPTON
GROUP TRENDS
As the nuclear charge increases, the electrons go into shells further from the nucleus.
Be
1s2 2s2
Mg
…3s2
Ca
… 4s2
Sr
… 5s2
2,2 2,8,2 2,8,8,2 2,8,18,8,2
New e/c
Old e/c
ELECTRONIC CONFIGURATION
4 12 20 38Atomic Number
Ba
… 6s2
2,8,18,18,8,2
56
©HOPTON
GROUP TRENDS
As the nuclear charge increases, the electrons go into shells further from the nucleus.
The extra distance of the outer shell from the nucleus affects…
Atomic radius Ionic radius Ionisation energy Melting point Chemical reactivity
Be
1s2 2s2
Mg
…3s2
Ca
… 4s2
Sr
… 5s2
2,2 2,8,2 2,8,8,2 2,8,18,8,2
New e/c
Old e/c
ELECTRONIC CONFIGURATION
4 12 20 38Atomic Number
Ba
… 6s2
2,8,18,18,8,2
56
©HOPTON
GROUP TRENDS
ATOMIC & IONIC RADIUS
Be Mg Ca Sr
0.106 0.140 0.174 0.191Atomic radius / nm
Ba
0.198
2,2 2,8,2 2,8,8,2 2,8,18,8,2Electronic config. 2,8,18,18,8,2
©HOPTON
GROUP TRENDS
ATOMIC RADIUS INCREASES down Group
• the greater the atomic number the more electrons there are; these go into shells increasingly further from the nucleus
ATOMIC & IONIC RADIUS
Be Mg Ca Sr
0.106 0.140 0.174 0.191Atomic radius / nm
Ba
0.198
2,2 2,8,2 2,8,8,2 2,8,18,8,2Electronic config. 2,8,18,18,8,2
1s2 2s2 2p6 3s2 1s2 2s2 2p6 3s23p64s2
©HOPTON
GROUP TRENDS
ATOMIC RADIUS INCREASES down Group
• the greater the atomic number the more electrons there are; these go into shells increasingly further from the nucleus
ATOMIC & IONIC RADIUS
Be Mg Ca Sr
0.106 0.140 0.174 0.191Atomic radius / nm
Ba
0.198
2,2 2,8,2 2,8,8,2 2,8,18,8,2Electronic config. 2,8,18,18,8,2
• atoms of Group II are smaller than the equivalent Group I atom
the extra proton exerts a greater attraction on the electrons
1s2 2s2 2p6 3s2 1s2 2s2 2p6 3s23p64s2
12 protons1s2 2s2 2p6 3s2
11 protons1s2 2s2 2p6 3s1
©HOPTON
GROUP TRENDS
ATOMIC & IONIC RADIUS
Be Mg Ca Sr
0.106 0.140 0.174 0.191Atomic radius / nm
Ba
0.198
2,2 2,8,2 2,8,8,2 2,8,18,8,2Electronic config. 2,8,18,18,8,2
Be2+ Mg2+ Ca2+ Sr2+
0.030 0.064 0.094 0.110Ionic radius / nm
Ba2+
0.134
2 2,8 2,8,8 2,8,18,8Electronic config. 2,8,18,18,8
©HOPTON
GROUP TRENDS
ATOMIC & IONIC RADIUS
Be Mg Ca Sr
0.106 0.140 0.174 0.191Atomic radius / nm
Ba
0.198
2,2 2,8,2 2,8,8,2 2,8,18,8,2Electronic config. 2,8,18,18,8,2
Be2+ Mg2+ Ca2+ Sr2+
0.030 0.064 0.094 0.110Ionic radius / nm
Ba2+
0.134
2 2,8 2,8,8 2,8,18,8Electronic config. 2,8,18,18,8
IONIC RADIUS INCREASES down Group
• ions are smaller than atoms – on removing the outer shell electrons, the remaining electrons are now in fewer shells
©HOPTON
GROUP TRENDS
ATOMIC & IONIC RADIUS
Be Mg Ca Sr
0.106 0.140 0.174 0.191Atomic radius / nm
Ba
0.198
2,2 2,8,2 2,8,8,2 2,8,18,8,2Electronic config. 2,8,18,18,8,2
Be2+ Mg2+ Ca2+ Sr2+
0.030 0.064 0.094 0.110Ionic radius / nm
Ba2+
0.134
2 2,8 2,8,8 2,8,18,8Electronic config. 2,8,18,18,8
IONIC RADIUS INCREASES down Group
• ions are smaller than atoms – on removing the outer shell electrons, the remaining electrons are now in fewer shells
1s2 2s2 2p6 3s2 1s2 2s2 2p6
©HOPTON
GROUP TRENDS
ATOMIC & IONIC RADIUS
Be Mg Ca Sr
0.106 0.140 0.174 0.191Atomic radius / nm
Ba
0.198
2,2 2,8,2 2,8,8,2 2,8,18,8,2Electronic config. 2,8,18,18,8,2
Be2+ Mg2+ Ca2+ Sr2+
0.030 0.064 0.094 0.110Ionic radius / nm
Ba2+
0.134
2 2,8 2,8,8 2,8,18,8Electronic config. 2,8,18,18,8
IONIC RADIUS INCREASES down Group
• ions are smaller than atoms – on removing the outer shell electrons, the remaining electrons are now in fewer shells
1s2 2s2 2p6 3s2 1s2 2s2 2p6 3s23p64s21s2 2s2 2p6 1s2 2s2 2p6 3s23p6
©HOPTON
GROUP TRENDS
MELTING POINT
Be Mg Ca Sr
2,2 2,8,2 2,8,8,2 2,8,18,8,2Electronic config.
1283 650 850 770Melting point / ºC
Ba
2,8,18,18,8,2
710
©HOPTON
GROUP TRENDS
DECREASES down Group
MELTING POINT
Be Mg Ca Sr
2,2 2,8,2 2,8,8,2 2,8,18,8,2Electronic config.
1283 650 850 770Melting point / ºC
Ba
2,8,18,18,8,2
710
©HOPTON
GROUP TRENDS
DECREASES down Group
• each atom contributes two electrons to the delocalised cloud
• metallic bonding gets weaker due to increased size of ion
MELTING POINT
Be Mg Ca Sr
2,2 2,8,2 2,8,8,2 2,8,18,8,2Electronic config.
1283 650 850 770Melting point / ºC
Ba
2,8,18,18,8,2
710
Larger ions mean that the electron
cloud doesn’t bind them as strongly
©HOPTON
GROUP TRENDS
DECREASES down Group
• each atom contributes two electrons to the delocalised cloud
• metallic bonding gets weaker due to increased size of ion
• Group I metals have lower melting points than the equivalent Group II metal because each metal only contributes one electron to the cloud
MELTING POINT
Be Mg Ca Sr
2,2 2,8,2 2,8,8,2 2,8,18,8,2Electronic config.
1283 650 850 770Melting point / ºC
Ba
2,8,18,18,8,2
710
Larger ions mean that the electron
cloud doesn’t bind them as strongly
©HOPTON
GROUP TRENDS
DECREASES down Group
• each atom contributes two electrons to the delocalised cloud
• metallic bonding gets weaker due to increased size of ion
• Group I metals have lower melting points than the equivalent Group II metal because each metal only contributes one electron to the cloud
NOTE Magnesium doesn’t fit the trend because crystalline structure can also affect the melting point of a metal
MELTING POINT
Be Mg Ca Sr
2,2 2,8,2 2,8,8,2 2,8,18,8,2Electronic config.
1283 650 850 770Melting point / ºC
Ba
2,8,18,18,8,2
710
Larger ions mean that the electron
cloud doesn’t bind them as strongly
©HOPTON
FIRST IONISATION ENERGY
©HOPTON
FIRST IONISATION ENERGY
Be Mg Ca Sr
899 738 590 550 1st I.E. / kJ mol-1
Ba
500
1800 1500 1100 1100 1000
14849 7733 4912 4120 3390
2nd I.E. / kJ mol-1
3rd I.E. / kJ mol-1
©HOPTON
FIRST IONISATION ENERGY
DECREASES down the GroupDespite the increasing nuclear charge the values decrease due to theextra shielding provided by additional filled inner energy levels
Be Mg Ca Sr
899 738 590 550 1st I.E. / kJ mol-1
Ba
500
1800 1500 1100 1100 1000
14849 7733 4912 4120 3390
2nd I.E. / kJ mol-1
3rd I.E. / kJ mol-1
©HOPTON
FIRST IONISATION ENERGY
DECREASES down the GroupDespite the increasing nuclear charge the values decrease due to theextra shielding provided by additional filled inner energy levels
Be Mg Ca Sr
899 738 590 550 1st I.E. / kJ mol-1
Ba
500
1800 1500 1100 1100 1000
14849 7733 4912 4120 3390
2nd I.E. / kJ mol-1
3rd I.E. / kJ mol-1
BERYLLIUMThere are 4 protons pulling on the outer shell electrons
1st I.E. = 899 kJ mol-1
4+
©HOPTON
FIRST IONISATION ENERGY
DECREASES down the GroupDespite the increasing nuclear charge the values decrease due to theextra shielding provided by additional filled inner energy levels
Be Mg Ca Sr
899 738 590 550 1st I.E. / kJ mol-1
Ba
500
1800 1500 1100 1100 1000
14849 7733 4912 4120 3390
2nd I.E. / kJ mol-1
3rd I.E. / kJ mol-1
BERYLLIUMThere are 4 protons pulling on the outer shell electrons
1st I.E. = 899 kJ mol-1
12+4+
MAGNESIUMThere are now 12 protons pulling on the outer shell
electrons. However, the extra filled inner shell shields the nucleus from the outer shell
electrons. The effective nuclear charge is less and the electrons are easier to remove.
1st I.E. = 738 kJ mol-1
©HOPTON
FIRST IONISATION ENERGY
DECREASES down the GroupDespite the increasing nuclear charge the values decrease due to theextra shielding provided by additional filled inner energy levels
Be Mg Ca Sr
899 738 590 550 1st I.E. / kJ mol-1
Ba
500
1800 1500 1100 1100 1000
14849 7733 4912 4120 3390
2nd I.E. / kJ mol-1
3rd I.E. / kJ mol-1
BERYLLIUMThere are 4 protons pulling on the outer shell electrons
1st I.E. = 899 kJ mol-1
12+4+
MAGNESIUMThere are now 12 protons pulling on the outer shell
electrons. However, the extra filled inner shell shield the
nucleus from the outer shell electrons. The effective
nuclear charge is less and the electrons are easier to remove.
1st I.E. = 738 kJ mol-1
©HOPTON
©HOPTON
SUCCESSIVE IONISATION ENERGIES
Successive Ionisation Energy values get larger
Be Mg Ca Sr
899 738 590 550 1st I.E. / kJ mol-1
Ba
500
1800 1500 1100 1100 1000
14849 7733 4912 4120 3390
2nd I.E. / kJ mol-1
3rd I.E. / kJ mol-1
©HOPTON
SUCCESSIVE IONISATION ENERGIES
Successive Ionisation Energy values get larger
Be Mg Ca Sr
899 738 590 550 1st I.E. / kJ mol-1
Ba
500
1800 1500 1100 1100 1000
14849 7733 4912 4120 3390
2nd I.E. / kJ mol-1
3rd I.E. / kJ mol-1
12+
1st I.E. = 738 kJ mol-1
©HOPTON
SUCCESSIVE IONISATION ENERGIES
Successive Ionisation Energy values get larger
Be Mg Ca Sr
899 738 590 550 1st I.E. / kJ mol-1
Ba
500
1800 1500 1100 1100 1000
14849 7733 4912 4120 3390
2nd I.E. / kJ mol-1
3rd I.E. / kJ mol-1
12+
1st I.E. = 738 kJ mol-1
12+
2nd I.E. = 1500 kJ mol-1
There are now 12 protons and only 11 electrons. The
increased ratio of protons to electrons means that it is
harder to pull an electron out.
©HOPTON
Successive Ionisation Energy values get larger
Be Mg Ca Sr
899 738 590 550 1st I.E. / kJ mol-1
Ba
500
1800 1500 1100 1100 1000
14849 7733 4912 4120 3390
2nd I.E. / kJ mol-1
3rd I.E. / kJ mol-1
12+
1st I.E. = 738 kJ mol-1
12+ 12+
2nd I.E. = 1500 kJ mol-1
There are now 12 protons and only 11 electrons. The
increased ratio of protons to electrons means that it is
harder to pull an electron out.
3rd I.E. = 7733 kJ mol-1
There is a big jump in IE because the electron being removed is
from a shell nearer the nucleus; there is less shielding.
SUCCESSIVE IONISATION ENERGIES
©HOPTON
Successive Ionisation Energy values get larger
Be Mg Ca Sr
899 738 590 550 1st I.E. / kJ mol-1
Ba
500
1800 1500 1100 1100 1000
14849 7733 4912 4120 3390
2nd I.E. / kJ mol-1
3rd I.E. / kJ mol-1
12+
1st I.E. = 738 kJ mol-1
12+ 12+
2nd I.E. = 1500 kJ mol-1
There are now 12 protons and only 11 electrons. The
increased ratio of protons to electrons means that it is
harder to pull an electron out.
3rd I.E. = 7733 kJ mol-1
There is a big jump in IE because the electron being removed is
from a shell nearer the nucleus; there is less shielding.
SUCCESSIVE IONISATION ENERGIES
©HOPTON
CHEMICAL PROPERTIES OF THE ELEMENTS
Reactivity increases down the Group due to the ease of cation formation
©HOPTON
CHEMICAL PROPERTIES OF THE ELEMENTS
Reactivity increases down the Group due to the ease of cation formation
OXYGEN react with increasing vigour down the group
Mg burns readily with a bright white flame
0 0 +2 -22Mg(s) + O2(g) —> 2MgO(s)
Ba burns readily with an apple-green flame
2Ba(s) + O2(g) —> 2BaO(s)
©HOPTON
CHEMICAL PROPERTIES OF THE ELEMENTS
Reactivity increases down the Group due to the ease of cation formation
OXYGEN react with increasing vigour down the group
Mg burns readily with a bright white flame
0 0 +2 -22Mg(s) + O2(g) —> 2MgO(s)
Ba burns readily with an apple-green flame
2Ba(s) + O2(g) —> 2BaO(s)
In both cases…
the metal is oxidised Oxidation No. increases from 0 to +2
oxygen is reduced Oxidation No. decreases from 0 to -2
Mg —> Mg2+ + 2e¯
O + 2e¯ —> O2-
©HOPTON
CHEMICAL PROPERTIES OF THE ELEMENTS
Reactivity increases down the Group due to the ease of cation formation
©HOPTON
CHEMICAL PROPERTIES OF THE ELEMENTS
Reactivity increases down the Group due to the ease of cation formation
WATER react with increasing vigour down the group
©HOPTON
CHEMICAL PROPERTIES OF THE ELEMENTS
Reactivity increases down the Group due to the ease of cation formation
WATER react with increasing vigour down the group
Mg reacts very slowly with cold water
Mg(s) + 2H2O(l) —> Mg(OH)2(aq) + H2(g)
but reacts quickly with steam
Mg(s) + H2O(g) —> MgO(s) + H2(g)
©HOPTON
CHEMICAL PROPERTIES OF THE ELEMENTS
Reactivity increases down the Group due to the ease of cation formation
WATER react with increasing vigour down the group
Mg reacts very slowly with cold water
Mg(s) + 2H2O(l) —> Mg(OH)2(aq) + H2(g)
but reacts quickly with steam
Mg(s) + H2O(g) —> MgO(s) + H2(g)
Ba reacts vigorously with cold water
Ba(s) + 2H2O(l) —> Ba(OH)2(aq) + H2(g)
©HOPTON
OXIDES OF GROUP II
Bonding • ionic solids; EXCEPT BeO which has covalent character
• BeO (beryllium oxide) MgO (magnesium oxide) CaO (calcium oxide) SrO (strontium oxide) BaO (barium oxide)
©HOPTON
OXIDES OF GROUP II
Bonding • ionic solids; EXCEPT BeO which has covalent character
• BeO (beryllium oxide) MgO (magnesium oxide) CaO (calcium oxide) SrO (strontium oxide) BaO (barium oxide)
Reactionwith water Be Mg Ca Sr
NONE reacts reacts reactsReactivity with water
Ba
reacts
Insoluble Sparinglysoluble
Slightlysoluble
Quitesoluble
Verysoluble
- 9-10
Solubility of hydroxide g/100cm3 of water
pH of solution
©HOPTON
OXIDES OF GROUP II
Bonding • ionic solids; EXCEPT BeO which has covalent character
• BeO (beryllium oxide) MgO (magnesium oxide) CaO (calcium oxide) SrO (strontium oxide) BaO (barium oxide)
Reactionwith water
React with water to produce the hydroxide (not Be)
e.g. CaO(s) + H2O(l) —> Ca(OH)2(s)
Be Mg Ca Sr
NONE reacts reacts reactsReactivity with water
Ba
reacts
Insoluble Sparinglysoluble
Slightlysoluble
Quitesoluble
Verysoluble
- 9-10
Solubility of hydroxide g/100cm3 of water
pH of solution
©HOPTON
HYDROXIDES OF GROUP II
Properties basic strength also increases down group
©HOPTON
HYDROXIDES OF GROUP II
Properties basic strength also increases down group
• this is because the solubility increases• the metal ions get larger so charge density decreases• get a lower attraction between the OH¯ ions and larger 2+ ions• the ions will split away from each other more easily• there will be a greater concentration of OH¯ ions in water
©HOPTON
HYDROXIDES OF GROUP II
Properties basic strength also increases down group
• this is because the solubility increases• the metal ions get larger so charge density decreases• get a lower attraction between the OH¯ ions and larger 2+ ions• the ions will split away from each other more easily• there will be a greater concentration of OH¯ ions in water
Be Mg Ca Sr
NONE reacts reacts reactsReactivity with water
Ba
reacts
Insoluble Sparinglysoluble
Slightlysoluble
Quitesoluble
Verysoluble
- 9-10
Solubility of hydroxide in water
pH of solution
©HOPTON
HYDROXIDES OF GROUP II
Properties basic strength also increases down group
• this is because the solubility increases• the metal ions get larger so charge density decreases• get a lower attraction between the OH¯ ions and larger 2+ ions• the ions will split away from each other more easily• there will be a greater concentration of OH¯ ions in water
Be Mg Ca Sr
NONE reacts reacts reactsReactivity with water
Ba
reacts
Insoluble Sparinglysoluble
Slightlysoluble
Quitesoluble
Verysoluble
- 9-10
Solubility of hydroxide in water
pH of solution
Lower charge density of the larger Ca2+ ion means that it doesn’t hold onto the
OH¯ ions as strongly. More OH¯ get released into the water. It is more soluble
and the solution has a larger pH.
©HOPTON
HYDROXIDES OF GROUP II
Uses
Ca(OH)2 used in agriculture to neutralise acid soils
Ca(OH)2(s) + 2H+ (aq) —> Ca2+(aq) + 2H2O(l)
Mg(OH)2 used in toothpaste and indigestion tablets as an antacid
Mg(OH)2(s) + 2H+ (aq) —> Mg2+(aq) + 2H2O(l)
Both the above are weak alkalis and not as caustic as sodium hydroxide
©HOPTON
CARBONATES OF GROUP II
©HOPTON
CARBONATES OF GROUP II
Properties
• insoluble in waterMgCO3 CaCO3 SrCO3 BaCO3
1.5 x 10-4 1.3 x 10-5 7.4 x 10-6 9.1 x 10-6Solubility g/100cm3 of water
©HOPTON
CARBONATES OF GROUP II
Properties
• insoluble in water
• undergo thermal decomposition to oxide and carbon dioxide e.g. MgCO3(s) —> MgO(s) + CO2(g)
MgCO3 CaCO3 SrCO3 BaCO3
1.5 x 10-4 1.3 x 10-5 7.4 x 10-6 9.1 x 10-6
980
Solubility g/100cm3 of water
Decomposition temperature / ºC 400 1280 1360
©HOPTON
CARBONATES OF GROUP II
Properties
• insoluble in water
• undergo thermal decomposition to oxide and carbon dioxide e.g. MgCO3(s) —> MgO(s) + CO2(g)
• the ease of decomposition decreases down the group
MgCO3 CaCO3 SrCO3 BaCO3
1.5 x 10-4 1.3 x 10-5 7.4 x 10-6 9.1 x 10-6
980
Solubility g/100cm3 of water
Decomposition temperature / ºC 400 1280 1360
©HOPTON
CARBONATES OF GROUP II
Properties
• insoluble in water
• undergo thermal decomposition to oxide and carbon dioxide e.g. MgCO3(s) —> MgO(s) + CO2(g)
• the ease of decomposition decreases down the group
MgCO3 CaCO3 SrCO3 BaCO3
1.5 x 10-4 1.3 x 10-5 7.4 x 10-6 9.1 x 10-6
980
Solubility g/100cm3 of water
Decomposition temperature / ºC 400 1280 1360
EASIER HARDER
©HOPTON
CARBONATES OF GROUP II
Properties
• insoluble in water
• undergo thermal decomposition to oxide and carbon dioxide e.g. MgCO3(s) —> MgO(s) + CO2(g)
• the ease of decomposition decreases down the group
MgCO3 CaCO3 SrCO3 BaCO3
1.5 x 10-4 1.3 x 10-5 7.4 x 10-6 9.1 x 10-6
980
Solubility g/100cm3 of water
Decomposition temperature / ºC 400 1280 1360
One might think that the greater charge density of the smaller Mg2+ would mean that it would hold onto the CO3
2- ion more and the ions would be more difficult to separate.
EASIER HARDER
©HOPTON
CARBONATES OF GROUP II
Properties
• insoluble in water
• undergo thermal decomposition to oxide and carbon dioxide e.g. MgCO3(s) —> MgO(s) + CO2(g)
• the ease of decomposition decreases down the group
MgCO3 CaCO3 SrCO3 BaCO3
1.5 x 10-4 1.3 x 10-5 7.4 x 10-6 9.1 x 10-6
980
Solubility g/100cm3 of water
Decomposition temperature / ºC 400 1280 1360
One might think that the greater charge density of the smaller Mg2+ would mean that it would hold onto the CO3
2- ion more and the ions would be more difficult to separate.
The driving force must be the formation of the oxide. The smaller ion with its greater charge density holds onto the O2- ion to make a more stable compound.
EASIER HARDER
©HOPTON
MgSO4 CaSO4 SrSO4 BaSO4
3.6 x 10-1 1.1 x 10-3 6.2 x 10-5 9.0 x 10-7Solubility g/100cm3 of water
GROUP TRENDS
SULPHATES
©HOPTON
MgSO4 CaSO4 SrSO4 BaSO4
3.6 x 10-1 1.1 x 10-3 6.2 x 10-5 9.0 x 10-7Solubility g/100cm3 of water
GROUP TRENDS
SULPHATES
SOLUBILITY DECREASES down the Group
• as the cation gets larger it has a lower charge density• it becomes less attracted to the polar water molecules
©HOPTON
MgSO4 CaSO4 SrSO4 BaSO4
3.6 x 10-1 1.1 x 10-3 6.2 x 10-5 9.0 x 10-7Solubility g/100cm3 of water
GROUP TRENDS
SULPHATES
SOLUBILITY DECREASES down the Group
• as the cation gets larger it has a lower charge density• it becomes less attracted to the polar water molecules
Greater charge density of Mg2+ ion means that it is more attracted to water
so the ionic lattice breaks up more easily
©HOPTON
MgSO4 CaSO4 SrSO4 BaSO4
3.6 x 10-1 1.1 x 10-3 6.2 x 10-5 9.0 x 10-7Solubility g/100cm3 of water
GROUP TRENDS
SULPHATES
SOLUBILITY DECREASES down the Group
• as the cation gets larger it has a lower charge density• it becomes less attracted to the polar water molecules
Greater charge density of Mg2+ ion means that it is more attracted to water
so the ionic lattice breaks up more easily
Lower charge density of larger Ca2+ means that it is less attracted to water so the ionic lattice breaks up less easily – IT IS LESS SOLUBLE
©HOPTON
MgSO4 CaSO4 SrSO4 BaSO4
3.6 x 10-1 1.1 x 10-3 6.2 x 10-5 9.0 x 10-7Solubility g/100cm3 of water
GROUP TRENDS
SULPHATES
SOLUBILITY DECREASES down the Group
• as the cation gets larger it has a lower charge density• it becomes less attracted to the polar water molecules
USE barium sulphate’s insolubility is used as a test for sulphates
Greater charge density of Mg2+ ion means that it is more attracted to water
so the ionic lattice breaks up more easily
Lower charge density of larger Ca2+ means that it is less attracted to water so the ionic lattice breaks up less easily – IT IS LESS SOLUBLE
©HOPTON