Topic 4:Inorganic chemistry

• The elements of Groups 1 and 2 follow a trend in ionisation energy down Group 2.
• Ionisation energy decreases down Group 2.
• Each element down Group 2 has an extra electron shell, which shields the outer electron from the attraction of the nucleus, making it easier to remove outer electrons.
• The trend in reactivity of the Group 2 elements down the group is that reactivity increases as the atomic radii increase, making it easier to remove outer electrons.
• Mg reacts in steam to produce magnesium oxide and hydrogen.
• Group 2 elements react with water to produce hydroxides.
• Mg(s) + H ₂ O(g) → MgO (s) + H ₂ (g)
• Mg will also react with warm water, giving magnesium hydroxide.
• Mg + 2H ₂ O → Mg(OH) ₂ + H ₂
• Group 2 elements react with oxygen to produce solid white oxides.
• The group 2 metals will burn in oxygen.
• Group 2 elements react with chlorine to produce solid white chlorides.
• The group 2 metals will react with chlorine.
• Mg + Cl ₂ → MgCl ₂
• Bubbling gas through limewater will turn it cloudy if CO ₂ is present.
• Carbonate ions, CO ₃ ² ⁻ , and hydrogencarbonate ions, HCO³ ⁻ , can be identified using an aqueous acid to form carbon dioxide.
• Sulfate ions, SO ₄ ² ⁻ , can be identified using acidified barium chloride solution.
• The presence of a carbonate or a hydrogencarbonate can be tested by adding any dilute acid and observing effervescence.
• Ba² ⁺ (aq) + SO ₄ ² ⁻ (aq) → BaSO ₄ (s) is the chemical equation for the reaction that forms BaSO ₄ (s) when Ba² ⁺ (aq) and SO ₄ ² ⁻ (aq) are combined.
• Hydrochloric acid is added to get rid of any trace of carbonate ions.
• Ammonium ions, NH4+, can be identified using sodium hydroxide solution and warming to form ammonia.
• Ammonia gas can be identified by its pungent smell or by turning damp red litmus paper blue.
• Fizzing due to CO ₂ would be observed if a carbonate or a hydrogencarbonate was present.
• If Barium Chloride is added to a solution that contains sulfate ions, a white precipitate will form.
• Testing for ammonium compounds involves testing for ammonium ion NH ⁴⁺ , by reaction by gently warming NaOH(aq) forming NH ₃ NH ⁴⁺ +OH ⁻ → NH ₃ + H ₂ O.
• MNO ₃ (s)→MNO(s) + O ₂ (g) is a decomposition reaction where Group 1 nitrates decompose to form the nitrate and oxygen.
• The elements of Group 7 (halogens) have trends in melting and boiling temperatures, physical state at room temperature, and electronegativity.
• As the electron drops back down from the higher to a lower energy level, energy is emitted in the form of visible light energy.
• As you go down Group 7, atomic radii increases due to the increasing number of electron shells, making the nucleus less able to attract the bonding pair of electrons, decreasing electronegativity.
• Nitrates decompose easily and can be tested by measuring how long it takes until a certain amount of oxygen is produced, enough to relight a glowing splint.
• The heat causes the electron to move to a higher energy level.
• Carbonates decompose easily and can be tested by measuring how long it takes for an amount of carbon dioxide to be produced.
• Flame tests involve using a nichrome wire, cleaning it by dipping in concentrated hydrochloric acid and then heating in a Bunsen flame, dipping it in solid and putting it in a Bunsen flame, and observing the flame.
• As you go down Group 7, there are more electrons and so more London forces can form between the molecules, increasing the melting and boiling points.
• The electron is unstable at the higher energy level and so drops back down.
• The flame colours for Groups 1 and 2 compounds can be determined by understanding experimental procedures to show patterns in thermal decomposition of Group 1 and 2 nitrates and carbonates.
• Understanding the formation of characteristic flame colours by Group 1 and 2 compounds involves understanding electron transitions.
• 2MNO ₃ (s) → 2MNO ₂ (s) + O ₂ (g) is a decomposition reaction where Group 2 nitrates decompose to form oxide, nitrogen dioxide and oxygen.
• Brown gas is a combination of NO ₂ and O ₂.
• Chlorine will displace both bromide and iodide ions.