New Way Chemistry for Hong Kong A-Level Book 41 1 Periodic Relationship among the Oxides, Chlorides and Simple Hydrides of the Elements Li to Cl 40.1Oxides 40.2Chlorides 40.3Simple Hydrides 40.4Periodicity in Stoichiometric Composition of Oxides, Chlorides and Hydrides of Periods 2 and 3 Elements Chapter 40

New Way Chemistry for Hong Kong A-Level Book Oxides (SB p.17) Periodicity in Nature of Bonding of Oxides The oxides of Periods 2 and 3 elements can be grouped into 3 types according to the nature of their bonding: 1.Ionic oxides; 2.Ionic oxides with high covalent character; 3.Covalent oxides

New Way Chemistry for Hong Kong A-Level Book Oxides (SB p.18) Period 2Li 2 OBeOB2O3B2O3 CO CO 2 N 2 O NO NO 2 N 2 O 4 N 2 O 5 O2O2 OF 2 Nature of bonding in the oxides Ionic Ionic with covalent character Covalent Period 3 Na 2 O Na 2 O 2 MgOAl 2 O 3 SiO 2 P 4 O 6 P 4 O 10 SO 2 SO 3 Cl 2 O Cl 2 O 7 Nature of bonding in the oxides Ionic Ionic with covalent character Covalent Periodicity in nature of bonding in the oxides of Periods 2 and 3 elements

New Way Chemistry for Hong Kong A-Level Book 44 4 Ionic Oxides Na 2 O(s) + H 2 O(l)  2NaOH(aq) Li 2 O(s) + H 2 O(l)  2LiOH(aq) MgO(s) + H 2 O(l)  Mg(OH) 2 (aq) 40.1 Oxides (SB p.18) Na 2 O 2 (s) + 2H 2 O(l)  2NaOH(aq) + H 2 O 2 (aq) MgO is less basic as Mg(OH) 2 is slightly soluble in water. Only a weakly alkaline solution formed. Periodicity in the Behaviour of Oxides in Water

New Way Chemistry for Hong Kong A-Level Book 45 5 Ionic Oxides with High Covalent Character BeO and Al 2 O 3 are amphoteric, and react with both acids and bases. Both are insoluble in water. BeO(s) + 2H + (aq)  Be 2+ (aq) + H 2 O(l) Al 2 O 3 (s) + 6H + (aq)  2Al 3+ (aq) + 3H 2 O(l) BeO(s) + 2OH – (aq) + H 2 O(l)  [Be(OH) 4 ] 2– (aq) beryllate ion Al 2 O 3 (s) + 2OH – (aq) + 3H 2 O(l)  2[Al(OH) 4 ] – (aq) aluminate ion 40.1 Oxides (SB p.19)

New Way Chemistry for Hong Kong A-Level Book Oxides (SB p.19) Covalent Oxides B 2 O 3 (s) + 3H 2 O(l)  2H 3 BO 3 (s) boric(III) acid Carbon monoxide is neutral and insoluble in water. CO 2 (g) + H 2 O(l)H 2 CO 3 (aq) carbonic acid Behaviour of Covalent Oxides of Elements in Period 2 in Water

New Way Chemistry for Hong Kong A-Level Book Oxides (SB p.19) Dinitrogen oxide and nitrogen oxide are neutral and insoluble in water. 2NO 2 (g) + H 2 O(l)  HNO 2 (aq) + HNO 3 (aq) coldnitric(III)nitric(V)acid N 2 O 4 (g) + H 2 O(l)  HNO 2 (aq) + HNO 3 (aq)

New Way Chemistry for Hong Kong A-Level Book Oxides (SB p.20) N 2 O 5 (s) + H 2 O(l)  2HNO 3 (aq) coldnitric(V) acid Oxygen difluoride is a colourless gas which hydrolyzes slowly to form oxygen and hydrogen fluoride OF 2 (g) + H 2 O(l)  2HF(aq) + O 2 (g) Oxygen is neutral and very slightly soluble in water.

New Way Chemistry for Hong Kong A-Level Book Oxides (SB p.19) SiO 2 (s) does not react with water. It is slightly acidic, and reacts with boiling alkalis to form silicates(IV) SiO 2 (s) + 2NaOH(aq)  Na 2 SiO 3 (aq) + H 2 O(l) Behaviour of Covalent Oxides of Elements in Period 3 in Water

New Way Chemistry for Hong Kong A-Level Book Oxides (SB p.20) P 4 O 6 reacts slowly 2P 4 O 6 (s) + 6H 2 O(l)  4H 3 PO 3 (aq) coldphosphoric(III) acid P 4 O 10 reacts vigorously 2P 4 O 10 (s) + 2H 2 O(l)  4HPO 3 (aq) coldpolyphosphoric(V) acid 2P 4 O 10 (s) + 6H 2 O(l)  4H 3 PO 4 (aq) warmphosphoric(V) acid

New Way Chemistry for Hong Kong A-Level Book Oxides (SB p.20) Cl 2 O(g) + H 2 O(l)  2HOCl(aq) chloric(I) acid SO 2 (g) + H 2 O(l) H 2 SO 3 (aq) sulphuric(IV) acid SO 3 (g) + H 2 O(l) H 2 SO 3 (aq) sulphuric(VI) acid Cl 2 O 7 (g) + H 2 O(l)  2HClO 4 (aq) chloric(VII) acid (very strong acid)

New Way Chemistry for Hong Kong A-Level Book Oxides (SB p.21) Period 2Li 2 OBeOB2O3B2O3 CO CO 2 N 2 O NO NO 2 N 2 O 4 N 2 O 5 O2O2 OF 2 Behaviour of oxides in water Reacts to form an alkaline solution of LiOH Does not react with water Reacts to form H 3 BO 3, which is a very weak acid CO: insoluble in water CO 2 : reacts to form H 2 CO 2, which is a very weak acid N 2 O and NO: insoluble in water NO 2 and N 2 O 4 : reacts to form an acidic solution of HNO 2 and HNO 3 N 2 O 5 : reacts with cold water to form HNO 3 Very slightly soluble in water, does not react with water Reacts slowly to form O 2 and an acidic solution of HF Acid/base nature of oxides Alkaline Ampho- teric Acidic NeutralAcidic

New Way Chemistry for Hong Kong A-Level Book Oxides (SB p.21) Period 3 Na 2 O Na 2 O 2 MgOAl 2 O 3 SiO 2 P 4 O 6 P 4 O 10 SO 2 SO 3 Cl 2 O Cl 2 O 7 Behaviour of oxides in water Na 2 O: reacts to form an alkaline solution of NaOH Na 2 O 2 : reacts to from NaOH and H 2 O 2 Reacts to form a weakly alkaline solution of Mg(OH) 2 Does not react with water P 4 O 6 : reacts to form H 3 PO 3 P 4 O 10 : reacts with cold water to form HPO 3 ; reacts with warm water to give H 3 PO 4 SO 2 : reacts to form an acidic solution of H 2 SO 3 SO 3 : reacts to form an acidic solution of H 2 SO 4 Cl 2 O: reacts to form an acidic solution of HOCl Cl 2 O 7 : reacts to form an acidic solution of HClO 4 Acid/base nature of oxides Alkaline Weakly alkaline AmphotericAcidic

New Way Chemistry for Hong Kong A-Level Book 414 Check Point 40-1 (a) Why does SiO 2 not react with water? Answer 40.1 Oxides (SB p.22) (a) SiO 2 does not react with water because the electronegativity values of silicon and oxygen are very similar, and the Si – O bond can be considered as non- polar. As a result, there is no positive centre for the lone pair electrons of the water molecule to attack.

New Way Chemistry for Hong Kong A-Level Book 415 Check Point 40-1 (b) Complete and balance the following equations. (i)K 2 O(s) + H 2 O(l)  (ii)BaO(s) + H 2 O(l)  (iii)Al 2 O 3 (s) + H 2 SO 4 (aq)  Answer 40.1 Oxides (SB p.22) (b)(i)K 2 O(s) + H 2 O(l)  2KOH(aq) (ii)BaO(s) + H 2 O(l)  Ba(OH) 2 (s) (iii)Al 2 O 3 (s) + 3H 2 SO 4 (aq)  Al 2 (SO 4 ) 3 (aq) + 3H 2 O(l)

New Way Chemistry for Hong Kong A-Level Book Chlorides (SB p.22) Periodicity in Nature of Bonding of Chlorides The chlorides of Period 2 and 3 elements can be grouped into 3 types according to the nature of their bonding: 1.Ionic chlorides; 2.Ionic chlorides with high covalent character; 3.Covalent chlorides

New Way Chemistry for Hong Kong A-Level Book Chlorides (SB p.22) Period 2LiClBeCl 2 BCl 3 CCl 4 NCl 3 Cl 2 OClF Nature of bonding in the chlorides Ionic Ionic with covalent character Covalent Period 3NaClMgCl 2 AlCl 3 SiCl 4 PCl 3 PCl 5 SCl 2 S 2 Cl 2 Cl 2 Nature of bonding in the chlorides Ionic Ionic with covalent character Covalent Periodicity in nature of bonding in the chlorides of Periods 2 and 3 elements

New Way Chemistry for Hong Kong A-Level Book 418 Ionic Chlorides 40.2 Chlorides (SB p.23) LiCl(s)  Li + (aq) + Cl – (aq) H2OH2O NaCl(s)  Na + (aq) + Cl – (aq) LiCl and NaCl dissolve in water but do not react with it H2OH2O MgCl 2 (s) + H 2 O(l)Mg(OH)Cl(s) + HCl(aq) MgCl 2 hydrolyzes slightly in water MgCl 2 · 6H 2 O(s)  Mg(OH)Cl(s) + HCl(g) + 5H 2 O(l) The hydrated crystal gives off HCl and leaves a basic salt when heated during hydrolysis  Periodicity in the Behaviour of Chlorides in Water

New Way Chemistry for Hong Kong A-Level Book 419 Ionic Chlorides with High Covalent Character BeCl 2 dissolves in water forming hydrated [Be(H 2 O) 4 ] 2+ species. This species hydrolyzes extensively in water. [Be(H 2 O) 4 ] 2+ (aq) + H 2 O(l)  [Be(H 2 O) 3 (OH)] + (aq) + H 3 O + (aq) 40.2 Chlorides (SB p.23) AlCl 3 hydrolyzes reversibly in water. AlCl 3 (s) + 6H 2 O(l) [Al(H 2 O) 6 ] 3+ (aq) + 3Cl – (aq)

New Way Chemistry for Hong Kong A-Level Book Chlorides (SB p.23) The hydrated aluminium ion will further dissociate to give an acidic solution. This is known as cation hydrolysis. [Al(H 2 O) 6 ] 3+ (aq) + H 2 O(l) [Al(H 2 O) 5 (OH)] 2+ (aq) + H 3 O + (aq) [Al(H 2 O) 5 (OH)] 2+ (aq) + H 2 O(l) [Al(H 2 O) 4 (OH) 2 ] + (aq) + H 3 O + (aq) [Al(H 2 O) 4 (OH) 2 ] + (aq) + H 2 O(l) [Al(H 2 O) 3 (OH) 3 ] (aq) + H 3 O + (aq)

New Way Chemistry for Hong Kong A-Level Book Chlorides (SB p.24) Covalent Chlorides BCl 3 (l) + 3H 2 O(l)  H 3 BO 3 (aq) + 3HCl(aq) boric(III) acid Tetrachloromethane is a non-polar molecule and immiscible with water. Also, carbon has no vacant d-orbitals. It does not react with water. NCl 3 (l) + H 2 O(l)  NH 3 (aq) + 3HOCl(aq) ammoniachloric(I) acid Behaviour of Covalent Chlorides of Elements in Period 2 in Water

New Way Chemistry for Hong Kong A-Level Book Chlorides (SB p.24) Cl 2 O(g) + H 2 O(l)  2HOCl(aq) chloric(I) acid Chlorine fluoride undergoes hydrolysis in water, forming hydrogen fluoride and chloric(I) acid ClF(g) + H 2 O(l)  HF(aq) + HOCl(aq) hydrogenchloric(I) acid fluoride

New Way Chemistry for Hong Kong A-Level Book Chlorides (SB p.24) PCl 3 (l) + 3H 2 O(l)  H 3 PO 3 (aq) + 3HCl(aq) coldphosphoric(III) acid PCl 5 reacts with water vigorously to form phosphorus oxychloride and is then hydrolyzed to phosphoric(V) acid Silicon(IV) chloride undergoes complete hydrolysis in water SiCl 4 (l) + 4H 2 O(l)  SiO 2 · 2H 2 O(s) + 4HCl(aq) Behaviour of Covalent Chlorides of Elements in Period 3 in Water

New Way Chemistry for Hong Kong A-Level Book Chloride (SB p.24) Sulphur dichloride and disulphur dichloride undergo hydrolysis in water SCl 2 (l) + H 2 O(l)  HSCl(aq) + HOCl(aq) S 2 Cl 2 (s) + 2H 2 O(l)  4HCl(aq) + SO 2 (g) + 3S(s) Chlorine undergoes hydrolysis in water to form an acidic solution Cl 2 (g) + H 2 O(l)  HCl(aq) + HOCl(aq) PCl 5 (s) + H 2 O(l)  POCl 3 (l) + 2HCl(aq) phosphorus oxychloride POCl 3 (l) + 3H 2 O(l)  H 3 PO 4 (aq) + 3HCl(aq) phosphoric(V) acid

New Way Chemistry for Hong Kong A-Level Book Chlorides (SB p.25) Period 2LiClBeCl 2 BCl 3 CCl 4 NCl 3 Cl 2 OClF Behaviour of chlorides in water Dissolves to give Li + and Cl – ions Dissolves to form [Be(H 2 O) 4 ] 2+ which is hydrolyzed to give an acidic solution of [Be(H 2 O) 3 (OH)] + Completely hydrolyzed to form an acidic solution of H 3 BO 3 Immiscible, does not react with water Completely hydrolyzed to form NH 3 and HOCl Reacts with water to form an acidic solution of HOCl Hydrolyzed to form an acidic solution of HF and HOCl Acid/base nature of chlorides NeutralAcidic Unclassified Acidic

New Way Chemistry for Hong Kong A-Level Book Chlorides (SB p.25) Period 3NaClMgCl 2 AlCl 3 SiCl 4 PCl 3 PCl 5 SCl 2 S 2 Cl 2 Cl 2 Behaviour of chlorides in water Dissolves to give Na + and Cl – ions Slightly hydrolyzed to form Mg(OH)Cl; the hydrated form (MgCl 2 6H 2 O) undergoes hydrolysis when heated to form Mg(OH)Cl and HCl Undergoes reversible hydrolysis to form [Al(H 2 O) 6 ] 3+ and Cl – Undergoes complete hydrolysis in water to form SiO 2 2H 2 O and HCl PCl 3 : instantly hydrolyzed by cold water to form H 3 PO 3 PCl 5 : hydrolyzed to form H 3 PO 4 SCl 2 : hydrolyzed to form an acidic solution of HSCl and HOCl S 2 Cl 2 : hydrolyzed to form HCl, SO 2 and S Hydrolyzed to form an acidic solution of HCl and HOCl Acid/base nature of chlorides Neutral Weakly acidic Acidic

New Way Chemistry for Hong Kong A-Level Book 427 Check Point 40-2 Give the equation for the reaction between each of the following compounds and water. (a)AlCl 3 (b)Cl 2 O 6 Answer 40.2 Chlorides (SB p.25) (a) AlCl 3 (s) + 6H 2 O(l)  [Al(H 2 O) 6 ] 3+ (aq) + 3Cl - (aq) [Al(H 2 O) 6 ] 3+ (aq) + H 2 O(l) [Al(H 2 O) 5 (OH)] 2+ (aq) + H 3 O + (aq) (b) Cl 2 O 6 (g) + H 2 O(l)  HClO 3 (aq) + HClO 4 (aq)

New Way Chemistry for Hong Kong A-Level Book Simple Hydrides (SB p.26) Periodicity in Nature of Bonding of Simple Hydrides The hydrides of Period 2 and 3 elements can be grouped into 3 types according to the nature of their bonding: 1.Ionic hydrides; 2.Covalent hydrides with some ionic character; 3.Typical covalent hydrides; 4.Polar covalent hydrides

New Way Chemistry for Hong Kong A-Level Book Simple Hydrides (SB p.26) Periodicity in nature of bonding in the hydrides of Periods 2 and 3 elements Period 2LiHBeH 2 B2H6B2H6 CH 4 NH 3 H2OH2OHF Nature of bonding in the hydrides Ionic Covalent with some ionic character Typical covalent Polar covalent Period 3NaHMgH 2 AlH 3 SiH 4 PH 3 H2SH2SHCl Nature of bonding in the hydrides Ionic Covalent with some ionic character Typical covalentPolar covalent

New Way Chemistry for Hong Kong A-Level Book 430 Ionic Hydrides NaH(s) + H 2 O(l)  NaOH(aq) + H 2 (g) LiH(s) + H 2 O(l)  LiOH(aq) + H 2 (g) 40.3 Simple Hydrides (SB p.27) LiH and NaH react with water to form an alkaline solution with the evolution of hydrogen gas. Periodicity in the Behaviour of Hydrides in Water

New Way Chemistry for Hong Kong A-Level Book 431 Covalent Hydrides with some Ionic Character MgH 2 (s) + 2H 2 O(l)  Mg(OH) 2 (s) + 2H 2 (g) BeH 2 (s) + 2H 2 O(l)  Be(OH) 2 (s) + 2H 2 (g) 40.3 Simple Hydrides (SB p.27) The solution formed is less alkaline as Be(OH) 2 and Mg(OH) 2 are slightly soluble in water AlH 3 (s) + 3H 2 O(l)  Al(OH) 3 (aq) + 3H 2 (g) B 2 H 6 (g) + 6H 2 O(l)  H 3 BO 3 (aq) + 6H 2 (g) B 2 H 6 is hydrolyzed to form boric acid while AlH 3 is hydrolyzed to give a slightly alkaline solution

New Way Chemistry for Hong Kong A-Level Book 432 Typical Covalent Hydrides 40.3 Simple Hydrides (SB p.27) Methane is immiscible with water and has no reaction with water SiH 4 (g) + 4H 2 O(l)  SiO 2 2H 2 O(s) + 4H 2 (g) Silane dissolves in water and is hydrolyzed slowly Phosphine is slightly basic and has no reaction with water

New Way Chemistry for Hong Kong A-Level Book 433 Polar Covalent Hydrides 40.3 Simple Hydrides (SB p.27) NH 3 (g) + H 2 O(l)NH 4 + (aq) + OH – (aq) Ammonia is a weak base HF(g) + H 2 O(l)H 3 O + (aq) + F – (aq) Hydrogen fluoride is a weak acid Behaviour of Polar Covalent Hydrides of Elements in Period 2 in Water

New Way Chemistry for Hong Kong A-Level Book Simple Hydrides (SB p.28) HCl(g) + H 2 O(l)  H 3 O + (aq) + Cl – (aq) HCl is very soluble in water and is a strong acid H 2 O(l) H 2 S(g) + H 2 O(l)H 3 O + (aq) + HS – (aq) H 2 S forms a weak acid H 3 O + (aq) + S 2– (aq) Behaviour of Polar Covalent Hydrides of Elements in Period 3 in Water

New Way Chemistry for Hong Kong A-Level Book Simple Hydrides (SB p.28) Period 2LiHBeH 2 B2H6B2H6 CH 4 NH 3 H2OH2OHF Behaviour of hydrides in water Reacts with water to form an alkaline solution of LiOH and H 2 Reacts with water to form an alkaline solution of Be(OH) 2 and H 2 Reacts with water to form an acidic solution of H 3 BO 3 and H 2 Does not react with water Dissolves to give NH 4 + and OH – —Dissolves to give H 3 O + and F – Acid/base nature of hydrides Alkaline AcidicNeutral Weakly alkaline Neutral Weakly acidic

New Way Chemistry for Hong Kong A-Level Book Simple Hydrides (SB p.28) Period 3NaHMgH 2 AlH 3 SiH 4 PH 3 H2SH2SHCl Behaviour of hydrides in water Reacts with water to form an alkaline solution of NaOH and H 2 Reacts with water to form an alkaline solution of Mg(OH) 2 and H 2 Reacts with water to form a slightly alkaline solution of Al(OH) 3 Slowly hydrolyzed by water to form SiO 2 2H 2 O and H 2 Does not react with water Reacts with water to form a weakly acidic solution Dissolves to give H 3 O + and Cl – Acid/base nature of hydrides Alkaline Slightly alkaline Essentially neutral Very slightly alkaline Weakly acidic Strongly acidic

New Way Chemistry for Hong Kong A-Level Book 437 Check Point 40-3 (a)(i)Describe the reaction of each of the following hydrides with water. Write appropriate equations. (1)NH 3 (2)HCl Answer 40.3 Simple Hydrides (SB p.29) (a)(i)(1)NH 3 reacts with water to give an alkaline solution. NH 3 (g) + H 2 O(l) NH 4 + (aq) + OH – (aq) (2)HCl reacts with water to form an acidic solution HCl(g) + H 2 O(l)  H 3 O + (aq) + Cl – (aq)

New Way Chemistry for Hong Kong A-Level Book 438 Check Point 40-3 (a)(ii)Explain why the above two hydrides react differently with water. Answer 40.3 Simple Hydrides (SB p.29) (a)(ii)The reason why the above two hydrides react differently with water is that ammonia molecule makes use of the lone pair electrons on the nitrogen atom to abstract the H + from a water molecule, leaving OH – ion. On the contrary, the hydrogen atom in the HCl molecule carries a partial positive charge, so it is abstracted by the lone pair electrons of the water molecule, thus forming hydroxonium ion.

New Way Chemistry for Hong Kong A-Level Book 439 Check Point 40-3 (b)Explain why CH 4 does not react with water. Answer 40.3 Simple Hydrides (SB p.29) (b)CH 4 does not react with water because the carbon atom of the molecule does not have lone pair electrons. Also, as the electronegativity values of carbon and hydrogen are very similar, the polarity of C – H bond is very small. Therefore, the hydrogen atom of CH 4 molecule cannot be abstracted by the lone pair electrons of the water molecule.

New Way Chemistry for Hong Kong A-Level Book Periodicity in Stoichiometric Composition of Oxides, Chlorides and Hydrides of Period 2 and 3 Elements (SB p.29) Period 2LiBeBCNOFNe Formulae of chlorides LiClBeCl 2 BCl 3 CCl 4 NCl 3 Cl 2 OClF— Formulae of oxides Li 2 OBeOB2O3B2O3 CO CO 2 N 2 O NO N 2 O 3 NO 2 N 2 O 4 N 2 O 5 O2O3O2O3 OF 2 — Formulae of hydrides LiHBeH 2 B2H6B2H6 C n H 2n+2 C n H 2n NH 3 H2OH2O2H2OH2O2 HF— Periodicity in stoichiometric composition of the oxides, chlorides and hydroxides of Period 2 elements

New Way Chemistry for Hong Kong A-Level Book Periodicity in Stoichiometric Composition of Oxides, Chlorides and Hydrides of Period 2 and 3 Elements (SB p.29) Period 3NaMgAlSiPSClAr Formulae of chlorides NaClMgCl 2 AlCl 3 SiCl 4 PCl 3 PCl 5 SCl 2 S 2 Cl 2 SCl 4 Cl 2 — Formulae of oxides Na 2 O Na 2 O 2 MgOAl 2 O 3 SiO 2 P 4 O 6 P 4 O 10 SO 2 SO 3 Cl 2 O ClO 2 Cl 2 O 6 Cl 2 O 7 — Formulae of hydrides NaHMgH 2 AlH 3 SiH 4 PH 3 H2SH2SHCl— Periodicity in stoichiometric composition of the oxides, chlorides and hydroxides of Period 3 elements

New Way Chemistry for Hong Kong A-Level Book Periodicity in Stoichiometric Composition of Oxides, Chlorides and Hydrides of Period 2 and 3 Elements (SB p.30) Across the period, number of oxygen, chlorine or hydrogen atom that combine with each atom of element increases. Reach the maximum at Group IVA Follow by decrease and reach the minimum at Group VIIA P, S and Cl have a wide range of oxidation states ∵ able to expand their octets by utilizing vacant 3d orbitals for bonding Observations:

New Way Chemistry for Hong Kong A-Level Book Periodicity in Stoichiometric Composition of Oxides, Chlorides and Hydrides of Period 2 and 3 Elements (SB p.30) P, S and Cl show their highest oxidation states in oxides or chloride but not hydrides ∵ oxygen and chlorine are much electronegative than hydrogen

New Way Chemistry for Hong Kong A-Level Book 444 The END