3rd Period (Na to Ar)

Physical and atomic properties

1.      Na – Mg – Al – Si – P – S – Cl – Ar

2.      Metallic radii for sodium, magnesium and aluminium.

3.      Covalent radii for silicon, phosphorus , sulphur and chlorine

4.      Van der wall radii for Argon.

5.      Ionization energy increase from left to right, exception→ Al and S.

6.      Electronegativity increases from left to right, exception → Ar

7.      Sodium , magnesium and aluminium are best conductors.

8.      Silicon is semiconductor.

9.      Phosphorus, sulphur, chlorine and argon are non-conductors.

10. Melting point and boiling point values increase up to Al and then decreases.

Reaction of 3^rd period elements with water, oxygen and chlorine

11. Magnesium and aluminium form layers when reacting with water.

12. Sodium undergoes exothermically reaction with cold water.

13. Magnesium reacts slowly with cold water and burn in steam producing Mg(OH)₂ and MgO.

14. Magnesium burnt in steam with its typical white flame.

15. Chlorine dissolves in water and produces green solution.

16. Reaction with

Metal	Water	Oxygen	Chlorine
Na	NaOH	Na2 O Na2 O2	NaCl
Mg	Mg (OH)2 MgO	MgO	MgCl2
Al	Al2 O3	Al2 O3	AlCl3
Si	Si O2	Si O2	SiCl4
P		P4 O6 P4 O10	PCl3 PCl5
S		SO2	S2Cl2
Cl	HCl + HOCl	Cl2O , Cl2O7

17. Sodium burns in oxygen with yellow flame.

18. Sodium forms normal oxide and also per oxides.

19. MgO and Al₂O₃ are of white colour.

20. Aluminium burns in oxygen when it is powdered.

21. Silicon will burn in oxygen if heated strongly well and SiO₂ is produced.

22. White phosphorus catch fire spontaneously in air with white flame and forms phosphorus (lll) oxide and phosphorus (lV) oxide.

23. Sulphur burns in oxygen with pale blue flame.

24. SO₂ is colourless.

25. PCl₃ → colourless fuming liquid

26. PCl₅  → straw colour solid

27. S₂Cl₂ → orange, foul smelling liquid

Formula of oxide Na2O MgO Al2O3 SiO2 P4O10 P4O6 SO3 SO2 Cl2O7 Cl2O State S S S S S L G L G Conductivity G G G v.poor Nill Nill Nill Strucuture Giant Giant Giant Giant Simple molecular Simple molecular Simple molecular Nature Basic Basic Amphoteric Acidic Acidic Acidic Acidic Metal oxides

Formula of oxide NaCl MgCl Al2Cl6 SiCl4 PCl3 S2Cl2 State S S S L L L G Conductivity G G v.poor NILL Nill Nill Strucuture Giant Giant Simple molecular Simple molecular Simple molecular Simple molecular Effect on adding water Solid dissolves readily Chlorides react and produces fumes of HCl

Formula of oxide Na2OH Mg(OH)2 Ca(OH2 Al2(OH)3 Si(OH)4 H3PO4 H2SO4 HClO4 Nature Basic Basic Amphoteric Acidic Acidic Acidic Acidic

Acid, Base Behavior of oxides;

28. Al₂O₃ does not react with but react with dilute acids and dilute alkali.

29. Al₂O₃ + 6H⁺ → 2Al³⁺ +3H₂O

30. Al₂O₃ + 2OH^- +3H₂O → 2 [Al (OH)₄ ] → aluminate ion

31. SiO₂ does not react with water, but it does react with concentrated alkalies forming silicates SiO₃^-2.

32. NO₂ react with water forming HNO₂ and HNO₃.

33. The oxides of P, S and Cl except ClO₂ react readily to form strongly acidic solution

34.  2HClO₄→ Perchloric acid

Reaction of oxides with water, acid and bases;

35. Metal oxides → Basic →Ionic

36. Non-Metal oxides → Acidic → Covalent

37. Normal oxides of most metal combine with acids to form salts. these are called basic oxides.

38. Basic oxides alts dissolve in water to give soluble hydroxides.

39. Acidic oxides are oxides of non-metals such as CO₂ and SO₂.

40. Acidic oxides react with bases to form salts and combine with water to form acids.

41. BeO and Al₂O₃ are amphoteric.

Sodium and magnesium hydroxides;

42. NaOH → soap, peteroleum and rubber industry

43. These are white solids having soapy touch.

44. Sodium hydroxides is only slightly soluble in water,

45. Sodium hydroxides is the most soluble substances in water evolving a considerable amount of heat due to the

46. formation of a number of hydrates such as NaOH.2H₂O

47. Magnesium hydroxide is obtained as white ppt when caustic potash us added to a soluble magnesium salt.

MgCl₂ + 2KOH → Mg(OH)₂ +2KCl

48. Solubility of Mg(OH)₂ is enhanced tremendously by the addition of NH₄Cl and NH₄OH is formed.

49. 2NH₄Cl → 2NH₄⁺ + 2Cl^-

50. Mg(OH)₂ → 2OH^- + Mg²⁺

51. 2NH₄⁺ +2OH^- → NH₄OH

Aluminium hydroxide

52. When an alkali is added to aquaseous solution of aluminium salts, alumiunium hydroxides get precipitated.

53. Al(SO₄)₃ +6NH₄OH →2 Al (OH)₃ + 3[ (NH₄)₂ SO₄]

54. The hydroxides is soluble in acids and caustic alkalies forming aluminates in the later.

55. 2 Al (OH)₃ + 2NaOH → 2Na[Al(OH)₄]

56. The Al (OH)₃ can  also be obtained by hydrolysis of AlCl₄ in excess water.

57. AlCl₃ + 3H₂O →Al(OH)₃ + 3HCl

58. The Al (OH)₃ has the ability to absorb various dyes forming colouring matter known as lakes.

Other hydroxides

59. Silicon hydroxide is a molecule with formula Si(OH)₄.

60. Si(OH)₄ is produced as;  SiO₂ + 2H₂O → Si(OH)₄ at 800 degree C.

61. Si(OH)₄ is unstable and form polymerizes.