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Periodic Variation in Physical Properties of the Elements H to Ar

38. Periodic Variation in Physical Properties of the Elements H to Ar. 38.1 The Periodic Table 38.2 Periodic Variation in Physical Properties of Elements. 38.1. The Periodic Table. 38.1 The Periodic Table (SB p.2). The Periodic Table. With more and more elements being discovered

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Periodic Variation in Physical Properties of the Elements H to Ar

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  1. 38 Periodic Variation in Physical Properties of the Elements H to Ar 38.1 The Periodic Table 38.2 Periodic Variation in Physical Properties of Elements

  2. 38.1 The Periodic Table

  3. 38.1 The Periodic Table (SB p.2) The Periodic Table • With more and more elements being discovered •  needed a way to organize them effectively

  4. 38.1 The Periodic Table (SB p.2) The Periodic Table • The modern Periodic Table •  the basis of the atomic numbers and electronic configurations of element

  5. 38.1 The Periodic Table (SB p.2) The modern Periodic Table

  6. 38.1 The Periodic Table (SB p.3) The Periodic Table • The earliest version of the Periodic Table •  introduced in 1869 •  by a Russian chemist called Dimitri Mendeleev

  7. 38.1 The Periodic Table (SB p.3) A portion of one of Dimitri Mendeleev’s handwritten drafts of the Periodic Table

  8. 38.1 The Periodic Table (SB p.3) Dimitri Mendeleev’s Periodic Table in 1872

  9. 38.1 The Periodic Table (SB p.3) The Periodic Table • Mendeleev created the first Periodic Table based on atomic masses • Many elements had similar properties •  occurred periodically •  the name Periodic Table was used

  10. 38.1 The Periodic Table (SB p.3) The Periodic Table • The periodic law stated •  the chemical and physical properties of the elements vary in a periodic way with their atomic masses

  11. 38.1 The Periodic Table (SB p.3) The Periodic Table • Example: • Lithium, sodium, potassium, rubidium and caesium •  have similarchemical properties

  12. 38.1 The Periodic Table (SB p.3) The Periodic Table • Example: • Beryllium, magnesium, calcium, strontium and barium •  also have similar chemical properties

  13. 38.1 The Periodic Table (SB p.3) The Periodic Table • According to Mendeleev’s theory •  they could be perfectly arranged by increasing atomic masses • Some elements did not matchperfectly

  14. 38.1 The Periodic Table (SB p.3) The Periodic Table • Tellurium is heavier than iodine •  but the chemical properties of tellurium did not match with those of chlorine and bromine •  the chemical properties of iodine did not match with those of sulphur and selenium

  15. 38.1 The Periodic Table (SB p.3) The Periodic Table • Tellurium should be placed before iodine •  even though tellurium was heavier than iodine

  16. Let's Think 1 38.1 The Periodic Table (SB p.3) The Periodic Table • The modern Periodic Table •  arranged according to atomic numbers instead of atomic masses

  17. 38.1 The Periodic Table (SB p.4) The Periodic Table • The modern Periodic Table is divided into •  7 horizontal rows called periods •  18 vertical columns called groups

  18. 38.1 The Periodic Table (SB p.4) The Periodic Table • Elements with atoms having the same number of electron shells •  put in the same period • Elements having the same number of outermost shell electrons •  put in the same group

  19. 38.1 The Periodic Table (SB p.4) The Periodic Table • Elements can be classified as • s-block elements • p-block elements • d-block elements • f-block elements

  20. 38.1 The Periodic Table (SB p.4) 1. s -Block Elements • Group IA and Group IIA elements constitute the s-block • They are elements with outermost shell electrons occupying the s orbital

  21. 38.1 The Periodic Table (SB p.4) 1. s -Block Elements • Group IA elements have only one outermost shell electron occupying the s orbital • Examples: • Lithium, sodium, potassium, rubidium, caesium and francium

  22. 38.1 The Periodic Table (SB p.4) 1. s -Block Elements • They are highly reactive metals • They areknown as the alkali metals

  23. 38.1 The Periodic Table (SB p.4) 1. s -Block Elements • Group IIA elements have two outermost shell electrons in the s orbital • Example: • Beryllium, magnesium, calcium, strontium, barium and radium

  24. 38.1 The Periodic Table (SB p.4) 1. s -Block Elements • They are also chemically reactive • They are known as the alkaline earth metals

  25. 38.1 The Periodic Table (SB p.4) 2. p -Block Elements • Elements having electronic configurations from [ ] ns2np1 to [ ] ns2np6 • They include Group IIIA, IVA, VA, VIA, VIIA and 0

  26. 38.1 The Periodic Table (SB p.4) 2. p -Block Elements • Group VIIA elements are all non-metals • They are known as the halogens

  27. 38.1 The Periodic Table (SB p.4) 2. p -Block Elements • Group 0 elements are called noble gases • They have a fully-filled outermost electron shell •  gives rise to extra stability •  the very stable electronic configuration

  28. 38.1 The Periodic Table (SB p.4) 2. p -Block Elements • s-Block and p-block elements together are also known as representative elements

  29. 38.1 The Periodic Table (SB p.4) 3. d -Block Elements • Elements with electronic configurations from [ ] (n – 1)d1ns2 (Group IIIB) to[ ] (n – 1)d10ns2 (Group IIB) • They are also called transition elements

  30. 38.1 The Periodic Table (SB p.4) 4. f -Block Elements • Two series of f-block elements in which the 4fand 5f orbitals being filled up with 1 to 14 electrons respectively • They are the lanthanide series and the actinide series • They are sometimes called inner-transition elements

  31. 38.1 The Periodic Table (SB p.5) Elements can be classified as s-block elements, p-block elements, d-block elements and f-block elements in the Periodic Table

  32. Check Point 38-1 38.1 The Periodic Table (SB p.5)

  33. 38.2 Periodic Variation in Physical Properties of Elements (SB p.6) First ionization enthalpy The first ionization enthalpy of an atom is the energy required to remove one mole of electrons from one mole of its gaseous atoms to form one mole of gaseous ions with one positive charge.

  34. 38.2 Periodic Variation in Physical Properties of Elements (SB p.6) First ionization enthalpy • Energy is required •  overcome the attractive forces between the nucleus and the electron to be removed •  the ionization enthalpy always has a positive value

  35. 38.2 Periodic Variation in Physical Properties of Elements (SB p.6) First ionization enthalpy • The ionization enthalpy of an element •  reflects the relative force of attraction between the nucleus and the electron being removed

  36. Let's Think 2 38.2 Periodic Variation in Physical Properties of Elements (SB p.6) First ionization enthalpy • Four main factors affecting the magnitude of the ionization enthalpy of an atom: • 1. the electronic configuration of an atom; • 2. the nuclear charge; • 3. the screening effect; and • 4. the atomic radius

  37. 38.2 Periodic Variation in Physical Properties of Elements (SB p.6) The first ionization enthalpies of the first 20 elements

  38. 38.2 Periodic Variation in Physical Properties of Elements (SB p.7) Variation in the first ionization enthalpy of the first 20 elements

  39. 38.2 Periodic Variation in Physical Properties of Elements (SB p.7) 1. General increase in the first ionization enthalpy across both Periods 2 and 3 • The consequence of the increase in nuclear charge with atomic numbers

  40. 38.2 Periodic Variation in Physical Properties of Elements (SB p.7) 1. General increase in the first ionization enthalpy across both Periods 2 and 3 • At the same time •  additional electrons are entering the same electron shell •  they have poor screening effect

  41. 38.2 Periodic Variation in Physical Properties of Elements (SB p.7) 1. General increase in the first ionization enthalpy across both Periods 2 and 3 • In other words •  an increase in effective nuclear charge across the periods

  42. 38.2 Periodic Variation in Physical Properties of Elements (SB p.7) 1. General increase in the first ionization enthalpy across both Periods 2 and 3 • Going across a period •  the electrons are drawn closer to the nucleus • more energy is required to remove an electron from the atom •  the first ionization enthalpy generally increases across both Periods 2 and 3

  43. 38.2 Periodic Variation in Physical Properties of Elements (SB p.7) 2. Irregularities with general increase in the first ionization enthalpy across both Periods 2 and 3 • In Period 2 •  the first ionization enthalpy of boron is lower than that of beryllium

  44. 38.2 Periodic Variation in Physical Properties of Elements (SB p.7) 2. Irregularities with general increase in the first ionization enthalpy across both Periods 2 and 3 • In Period 3 •  the first ionization enthalpy of aluminium is lower than that of magnesium

  45. 38.2 Periodic Variation in Physical Properties of Elements (SB p.7) 2. Irregularities with general increase in the first ionization enthalpy across both Periods 2 and 3 • Boron and aluminium have [ ] ns2np1 electronic configurations •  easier to remove the outermost p electron

  46. 38.2 Periodic Variation in Physical Properties of Elements (SB p.7) 2. Irregularities with general increase in the first ionization enthalpy across both Periods 2 and 3  the electron is shielded from the attraction of the nucleus by the completely filleds orbitals (ns2)  The first ionization enthalpies of Group III elements are not very high

  47. 38.2 Periodic Variation in Physical Properties of Elements (SB p.7) 2. Irregularities with general increase in the first ionization enthalpy across both Periods 2 and 3 • Beryllium and magnesium have a relatively stable electronic configuration •  the s orbital is completely filled •  a relatively large amount of energy is needed to ionize their atoms

  48. 38.2 Periodic Variation in Physical Properties of Elements (SB p.7) 2. Irregularities with general increase in the first ionization enthalpy across both Periods 2 and 3 • In Period 2 •  the first ionization enthalpy of oxygen is lower than that of nitrogen

  49. 38.2 Periodic Variation in Physical Properties of Elements (SB p.7) 2. Irregularities with general increase in the first ionization enthalpy across both Periods 2 and 3 • In Period 3 •  the first ionization enthalpy of sulphur is lower than that of phosphorus

  50. 38.2 Periodic Variation in Physical Properties of Elements (SB p.7) 2. Irregularities with general increase in the first ionization enthalpy across both Periods 2 and 3 • The atoms of oxygen and sulphur have one electron more than the half-filled p sub-shell •  when the electronic configuration of half-filledp sub-shell (np3) is attained • extra stability is gained

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