Topic 4 – Inorganic Chemistry and the Periodic Table
In order to develop their practical skills, students should be encouraged to carry out a range of practical experiments related to this topic. Possible
experiments include reacting Group 2 elements with water, heating nitrates and carbonates of Group 1 and 2 elements, investigating flame colours
of s-block elements, preparing iodine from seaweed, investigating displacement reactions in the halogens, reacting Group 1 halides with
concentrated sulfuric acid. Mathematical skills that could be developed in this topic include manipulating data on the solubility of hydroxides. Within
this topic, students can consider how data can be used to make predictions based on patterns and relationships, for example by predicting
properties of Group 7 elements.
Topic 4A: The elements of Groups 1 and 2
1. understand reasons for the trend in ionisation energy down Group 2
Explain why first ionisation energy decreases down Group 2.
Although the nuclear charge is increasing down the group, the atomic radius also increases, as is the shielding from
inner shell electrons. Since the outer shell electrons are further from the nucleus, the pull of the nucleus is reduced so
it becomes easier to remove the outer electron, so less energy is required to separate the two.
2. understand reasons for the trend in reactivity of the Group 2 elements down the group
Explain why reactivity increases down Group 2.
Apart from beryllium, all Group 2 elements react with other chemicals to form a 2+ ion. Reactivity increases down
Group 2 because their ionisation energy decreases – i.e. it becomes easier for a metal to lost electrons to form a
cation. For the reasons why the ionisation energy decreases, see above.
3. know the reactions of the elements Mg to Ba in Group 2 with oxygen, chlorine and water
State what you would see if a Group 2 element reacted with oxygen. Are there any exceptions?
Group 2 elements react vigorously with oxygen, usually producing a bright white flame. A white ionic/basic oxide is
usually formed as a result. However, beryllium does not react with oxygen, and barium reacts to form a peroxide.
Give the balanced symbol equation for the reaction between magnesium and oxygen.
2Mg(s) + O2 (g) -> 2MgO(s)
What product is formed when Group 2 metals react with chlorine?
Ionic chlorides form when Group 2 metals are
heated with chlorine. The only exception is
beryllium (again!), which forms a covalent
chloride. This has a polymeric structure where
the linear BeCl2 molecules are joined by dative
covalent bonds. THE DIMER LOOKS LIKE Al2Cl3!!
Explain the reaction that occurs when Group 2 metals react with water, and any exceptions.
Group 2 metals generally react with water to form hydrogen gas and metal hydroxides. Beryllium has NO reaction
with water due to a thick oxide layer of BeO. Magnesium reacts very slowly (but reacts w/ steam to make the oxide).
Calcium, strontium and barium react rapidly with cold water, and their hydroxides become more soluble down the
group. Calcium reacts to produce a white suspension of the hydroxide.
, 4. know the reactions of the oxides of Group 2 elements with water and dilute acid, and their hydroxides
with dilute acid
Describe the reaction that occurs when Group 2 oxides react with water, and any exceptions. Give an equation.
Group 2 oxides react with water to form hydroxides. Beryllium oxide does not react and magnesium oxide reacts very
slowly. An example is SrO(s) + H2O(l) -> Sr(OH)2 (aq), or SrO(s) + H2O(l) -> Sr2+(aq) + 2OH-(aq).
How do Group 2 peroxides react with water?
These react to form the metal hydroxide and hydrogen peroxide. BaO2 + 2H2O -> Ba(OH)2 + H2O2.
Write the balanced symbol equation for the reaction between strontium oxide and nitric acid.
SrO(s) + 2HNO3 (aq) -> Sr(NO3)2 (aq) + H2O(l)
Explain the differences between Group 2 oxides and hydroxides regarding how they react with acids.
No difference in terms of products produced. They just make more water.
Write the balanced symbol equation for the reaction between magnesium hydroxide and hydrochloric acid.
Mg(OH2)(s) + 2HCl(aq) -> MgCl2 (aq) + 2H2O(l)
Describe how calcium hydroxide is used to test for carbon dioxide.
Bubble the carbon dioxide through the limewater (Ca(OH) 2 (aq)), the limewater will turn cloudy/milky white due to a
suspension of calcium carbonate forming. Ca(OH)2 (aq) + CO2 (g) -> CaCO3 (s) + H2O(l)
5. know the trends in solubility of the hydroxides and sulfates of Group 2 elements
State the trend in solubility of Group 2 hydroxides.
Solubility of Hydroxides Increases Down Group (SHID – imagine an Australian man is talking to you about his shed)
What is the trend in solubility of Group 2 sulfates?
Solubility of sulfates decreases down the group – remember barium sulfate (from the ion test) is very insoluble.
6. understand reasons for the trends in thermal stability of the nitrates and the carbonates of the elements
in Groups 1 and 2 in terms of the size and charge of the cations involved
Explain the trend in thermal stability of Group 1/2 carbonates and nitrates.
Group 2 carbonates/nitrates are more thermally stable as you go down the group. As the cations get bigger, their
charge density decreases. So they have less of a polarising effect and distort the anion less. This has less of a
weakening effect on the C-O/N-O bond, so the anion breaks up less easily.
7. understand the formation of characteristic flame colours by Group 1 and 2 compounds in terms of
electron transitions. Students will be expected to know the flame colours for Groups 1 and 2 compounds.
Give the flame colours of the Group 1 metals.
Lithium – bright red Sodium – yellow Potassium – lilac
Give the flame colours of the Group 2 metals.
Calcium – brick red Strontium – bright red Barium – apple green
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In order to develop their practical skills, students should be encouraged to carry out a range of practical experiments related to this topic. Possible
experiments include reacting Group 2 elements with water, heating nitrates and carbonates of Group 1 and 2 elements, investigating flame colours
of s-block elements, preparing iodine from seaweed, investigating displacement reactions in the halogens, reacting Group 1 halides with
concentrated sulfuric acid. Mathematical skills that could be developed in this topic include manipulating data on the solubility of hydroxides. Within
this topic, students can consider how data can be used to make predictions based on patterns and relationships, for example by predicting
properties of Group 7 elements.
Topic 4A: The elements of Groups 1 and 2
1. understand reasons for the trend in ionisation energy down Group 2
Explain why first ionisation energy decreases down Group 2.
Although the nuclear charge is increasing down the group, the atomic radius also increases, as is the shielding from
inner shell electrons. Since the outer shell electrons are further from the nucleus, the pull of the nucleus is reduced so
it becomes easier to remove the outer electron, so less energy is required to separate the two.
2. understand reasons for the trend in reactivity of the Group 2 elements down the group
Explain why reactivity increases down Group 2.
Apart from beryllium, all Group 2 elements react with other chemicals to form a 2+ ion. Reactivity increases down
Group 2 because their ionisation energy decreases – i.e. it becomes easier for a metal to lost electrons to form a
cation. For the reasons why the ionisation energy decreases, see above.
3. know the reactions of the elements Mg to Ba in Group 2 with oxygen, chlorine and water
State what you would see if a Group 2 element reacted with oxygen. Are there any exceptions?
Group 2 elements react vigorously with oxygen, usually producing a bright white flame. A white ionic/basic oxide is
usually formed as a result. However, beryllium does not react with oxygen, and barium reacts to form a peroxide.
Give the balanced symbol equation for the reaction between magnesium and oxygen.
2Mg(s) + O2 (g) -> 2MgO(s)
What product is formed when Group 2 metals react with chlorine?
Ionic chlorides form when Group 2 metals are
heated with chlorine. The only exception is
beryllium (again!), which forms a covalent
chloride. This has a polymeric structure where
the linear BeCl2 molecules are joined by dative
covalent bonds. THE DIMER LOOKS LIKE Al2Cl3!!
Explain the reaction that occurs when Group 2 metals react with water, and any exceptions.
Group 2 metals generally react with water to form hydrogen gas and metal hydroxides. Beryllium has NO reaction
with water due to a thick oxide layer of BeO. Magnesium reacts very slowly (but reacts w/ steam to make the oxide).
Calcium, strontium and barium react rapidly with cold water, and their hydroxides become more soluble down the
group. Calcium reacts to produce a white suspension of the hydroxide.
, 4. know the reactions of the oxides of Group 2 elements with water and dilute acid, and their hydroxides
with dilute acid
Describe the reaction that occurs when Group 2 oxides react with water, and any exceptions. Give an equation.
Group 2 oxides react with water to form hydroxides. Beryllium oxide does not react and magnesium oxide reacts very
slowly. An example is SrO(s) + H2O(l) -> Sr(OH)2 (aq), or SrO(s) + H2O(l) -> Sr2+(aq) + 2OH-(aq).
How do Group 2 peroxides react with water?
These react to form the metal hydroxide and hydrogen peroxide. BaO2 + 2H2O -> Ba(OH)2 + H2O2.
Write the balanced symbol equation for the reaction between strontium oxide and nitric acid.
SrO(s) + 2HNO3 (aq) -> Sr(NO3)2 (aq) + H2O(l)
Explain the differences between Group 2 oxides and hydroxides regarding how they react with acids.
No difference in terms of products produced. They just make more water.
Write the balanced symbol equation for the reaction between magnesium hydroxide and hydrochloric acid.
Mg(OH2)(s) + 2HCl(aq) -> MgCl2 (aq) + 2H2O(l)
Describe how calcium hydroxide is used to test for carbon dioxide.
Bubble the carbon dioxide through the limewater (Ca(OH) 2 (aq)), the limewater will turn cloudy/milky white due to a
suspension of calcium carbonate forming. Ca(OH)2 (aq) + CO2 (g) -> CaCO3 (s) + H2O(l)
5. know the trends in solubility of the hydroxides and sulfates of Group 2 elements
State the trend in solubility of Group 2 hydroxides.
Solubility of Hydroxides Increases Down Group (SHID – imagine an Australian man is talking to you about his shed)
What is the trend in solubility of Group 2 sulfates?
Solubility of sulfates decreases down the group – remember barium sulfate (from the ion test) is very insoluble.
6. understand reasons for the trends in thermal stability of the nitrates and the carbonates of the elements
in Groups 1 and 2 in terms of the size and charge of the cations involved
Explain the trend in thermal stability of Group 1/2 carbonates and nitrates.
Group 2 carbonates/nitrates are more thermally stable as you go down the group. As the cations get bigger, their
charge density decreases. So they have less of a polarising effect and distort the anion less. This has less of a
weakening effect on the C-O/N-O bond, so the anion breaks up less easily.
7. understand the formation of characteristic flame colours by Group 1 and 2 compounds in terms of
electron transitions. Students will be expected to know the flame colours for Groups 1 and 2 compounds.
Give the flame colours of the Group 1 metals.
Lithium – bright red Sodium – yellow Potassium – lilac
Give the flame colours of the Group 2 metals.
Calcium – brick red Strontium – bright red Barium – apple green
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