08. classification 1


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  • 4s1 4s2,4p2- Ge 4d4,5s1- Nb 4f2,5d0,6s2-Ce
  • 08. classification 1

    1. 1. Chemistry
    2. 2. Session Opener
    3. 3. 1. Why do we need classification.? 2. Dobereniner’s triads 3. Newlands law of octave 4. Lother Meyer volume curve 5. Mendeleev’s periodic table 6. Modern periodic table 7. IUPAC nomenculature for elements Z >100 Session Objectives
    4. 4. Lavoisier (1789) classified elements into metals, non-metals, gases and earths. Do you know During the nineteenth century, chemists began to categorize the elements according to similarities in their physical and chemical properties. The end result of these studies was our modern periodic table.
    5. 5. S.No Triad Atomic masses of elements of triad Arithmetic mean of atomic masses of first and third element 1 Cl,Br,I 35.5, 80, 127 35.5 + 127 2 = 81.25 2 Li,Na,K 7, 23, 39 7 + 39 2 = 23 3 Ca,Sr,Ba 40,87.5,137 40+137 2 = 88.5 Dobereiner’s triads [ John Dobereiner (1829)] In 1829, he classified some elements into groups of three, which he called triads. The elements in a triad had similar chemical properties and orderly physical properties. Model of triads
    6. 6. John Newlands 1838 - 1898 Law of Octaves In 1863, he suggested that elements be arranged in “octaves” because he noticed (after arranging the elements in order of increasing atomic mass) that certain properties repeated every 8th element.
    7. 7. Newland’s law of octaves [John Newland (1862)] Element Atomic mass Element Atomic mass Element Atomic mass I II III IV V VI VII Li Be B C N O F 7 9 11 12 14 16 19 Na Mg Al Si p S Cl 23 24 27 28 31 32 35.5 K Ca 39 40
    8. 8. Newland was first to publish the list of elements in increasing order of atomic masses. Do you know?
    9. 9. Lother-Meyer’s atomic volume curve [Lother Meyer (1869)]
    10. 10. Question
    11. 11. If elements A,B and Z occupy similar positions in Lother meyer curve, they will have----properties (a)Different (b)Similar (c)Cannot say Illustrative Problem
    12. 12. The physical and chemical properties of elements are periodic function of their atomic masses. Mendeleev’s periodic law
    13. 13. Mendeleev’s periodic table
    14. 14. Groups •8 vertical rows. •7 groups were subdivided in A and B. •8th group has 9 elements in the group of 3 each. Periods •7 horizontal rows. Only 63 elements were known. Mendeleev’s periodic table
    15. 15. Merits of Mendeleev’s periodic table Prediction of new elements (Ge, Ga, Sc) 1 Systematic study of elements 2 Correction of atomic mass (Be, Au, Pt) 3
    16. 16. Defects of Mendeleev’s periodic table Position of hydrogen. Anomalous pairs. (Ar and K, Co and Ni, Te and I) Position of isotopes e.g. 1H1, 1H2, 1H3
    17. 17. Chemically dissimilar elements are grouped together. (Cu-IA and Na-IB) Chemically similar elements are placed in different groups. [Cu (I) and Hg (II)]. Defects of Mendeleev’s periodic table
    18. 18. Question
    19. 19. Mendeleev gave more importance to -----while arranging the elements in long form of periodic table (a)atomic mass (b)atomic volume (c)atomic number (d)similarity in property Illustrative Problem Solution: Option (a) is correct.
    20. 20. Mendeleev’s periodic table was published in 1905 when no one had an idea of the structure of an atom. Do you know?
    21. 21. The physical and chemical properties of elements are periodic function of their atomic numbers. Modern periodic law (Moseley)
    22. 22. Modern periodic table
    23. 23. Quiz Write the electronic configuration of elements having following atomic numbers. (a). 19 (b). 32 (c). 41 (d). 58
    24. 24. • Electronic configuration: • Groups: • Low ionisation energy and low melting and boiling points, electropositive elements. • Colourless compounds. s block elements IA and IIA ns1 or ns2
    25. 25. • Electronic configuration: • Groups: • Non-metals, electronegative. • Form covalent compounds. p block elements ns2 ,np1-6 III A to VII A and zero group.
    26. 26. • Electronic configuration: • Groups: • Variable valency high melting and boiling point. • Coloured compounds and catalytic property. d block elements (n-1)d1-10 ns1or2 I B to VII B and VIII groups.
    27. 27. • Electronic configuration: • Have high melting and boiling point. f block elements (n-2)f1-14 (n-1)d0-1 ns2 •Present below the periodic table in two rows •Lanthanides-elements after lanthanum •Actinides-elements after actinium.
    28. 28. Features of long form of periodic table •Contains elements arranged in increasing order of atomic numbers. •Explains the position of an element in relation to other elements. •Consists of groups and periods.
    29. 29. Features of long form of periodic table Groups Vertical column Total 18. Numbered 1-18 or IA to VII A, IB to VII B, VIII and zero. Periods Horizontal column Total 7 numbered from 1 to 7. Elements in a group have similar but not identical electronic configuration and properties Contains 2,8,8,18,18,32 and 28 elements respectively.
    30. 30. Representative elements Transition elements s and p block elements . d block elements. Valence shell and penultimate shell both are incomplete. Inner Transition elements f block elements. Valence shell, penultimate shell antipenultimate shell are incomplete. Features of long form of periodic table
    31. 31. Metals •Present on left hand side of periodic table. •Solid,malleable,ductile and conductors . Non-metals •Present on right hand side of periodic table. •Solid or liquid or gas. Metalloids •Present on zig-zag between metals and non-metals. e.g. B,Si,Ge,As,Sb and Te. Features of long form of periodic table
    32. 32. • Based on a more fundamental basis - the atomic number • Position of an element is related to the electronic configuration of its atom. • Due to separation of elements into groups, dissimilar elements (e.g. alkali metals I A and coinage metals I B) do not fall together. Merits of long form of periodic table
    33. 33. Defects of long form of periodic table The problem of the position of hydrogen in the table has not been solved completely Configuration of Helium(1s2 ) is different from inert gases (ns2 ,np6 ) but are placed in the same group. It is unable to include lanthanides and actinides in its main body.
    34. 34. Digits Name Abbreviation 0 nil n 1 un u 2 bi b 3 tri t 4 quad q 5 pent p 6 hex h 7 sept s 8 oct o 9 enn e e.g. atomic number 115 will be named as un+un+pent+ium =ununpentium and symbol is Uup Name=digits name+ium Nomenclature of the elements with atomic number>100
    35. 35. Class Test
    36. 36. Class Exercise - 1 X, Y and Z are the elements of Dobereiner’s triad. If atomic mass of element X is 32 and that of element Z is 128, find the atomic mass of Y. (a) 32 (b) 80 (c) 128 (d) 160 Solution The question is based on Dobereiner’s law of triads. Atomic mass of element Y =∴ + = = 32 128 160 80 2 2 Hence, answer is (b).
    37. 37. Class Exercise - 2 Newland’s law of octave is applied to all the elements having atomic mass less than ______. (a) 20 (b) 40 (c) 30 (d) 10 Solution: Hence, answer is (b). From Newland’s law of Octave.
    38. 38. Class Exercise - 3 Discovery of _________ is responsible for failure of law of octave. (a) lanthanides (b) actanides (c) transition elements (d) noble gases Hence, answer is (d). From Newland’s law of Octave. Solution:
    39. 39. Class Exercise - 4 Properties of element E are similar to that of element T. If element T is present on ascending side of Lother Meyer graph, where will you find element E? (a) on descending side (b) on peak (c) on ascending side (d) None of these The elements having similar properties occupy similar positions on the Lother Meyer volume curve. Hence, answer is (c). Solution:
    40. 40. Class Exercise - 5 How many elements were know when Mendeleev prepared his periodic table? (a) 53 (b) 63 (c) 51 (d) 76 Hence, answer is (b). Mendeleev’s periodic table based on 63 elements. Solution:
    41. 41. Class Exercise - 6 The valence shell electronic configuration of an element is [Rn] 7s2 6d5 5f14 . The element belongs to (a) actinide series (b) lanthanide series (c) 6d transition series (d) p block Hence, answer is (c). Because last electron enters into d subshell of penultimate orbit. Solution:
    42. 42. Class Exercise - 7 Which of the following groups have chemical properties that are most similar? (a) N, O, S (b) Na, K, Rb (c) Na, Mg, Ca (d) Na, Rb, Mg Hence, answer is (b). Because they belong to same group. (IA) Solution:
    43. 43. Class Exercise - 8 In which orbitals does the differentiating electron enters in case of inner transition elements? (a) (n – 1)d (b) ns1 (c) ns2 , np1–6 (d) (n – 2)f Hence, answer is (d). f-block elements are known as inner-transition elements. Solution:
    44. 44. Class Exercise - 9 The mass number of is (a) 50 (b) 112 (c) 118 (d) 62 112 50 Sn Hence, answer is (b). Mass number = number of proton + number of neutron = 50 + (112 – 50) = 50 + 62 = 112 Solution:
    45. 45. Class Exercise - 10 The name of element having atomic number 101 is (a) Rutherfordium (b) Lawrencium (c) Hassium (d) Mendelevium Hence, answer is (d). Rutherfordium – 104 Lawrencium – 103 Hassium – 108 Solution:
    46. 46. Illustrative example (a).His law of octaves failed beyond the element calcium. Why? (b). Would his law of octaves work today with the first 20 elements?
    47. 47. Dmitri Mendeleev 1834 - 1907 In 1869 he published a table of the elements organized by increasing atomic mass.
    48. 48. Lothar Meyer 1830 - 1895 At the same time, he published his own table of the elements organized by increasing atomic mass. •Both Mendeleev and Meyer arranged the elements in order of increasing atomic mass. •Both left vacant spaces where unknown elements should fit.
    49. 49. So why is Mendeleev called the “father of the modern periodic table” and not Meyer, or both? Illustrative example •stated that if the atomic weight of an element caused it to be placed in the wrong group, then the weight must be wrong. (He corrected the atomic masses of Be, In, and U) •was so confident in his table that he used it to predict the physical properties of three elements that were yet unknown. Solution: After the discovery of these unknown elements between 1874 and 1885, and the fact that Mendeleev’s predictions for Sc, Ga, and Ge were amazingly close to the actual values, his table was generally accepted.
    50. 50. However, in spite of Mendeleev’s great achievement, problems arose when new elements were discovered and more accurate atomic weights determined. By looking at our modern periodic table, can you identify what problems might have caused chemists a headache? Ar and K Co and Ni Te and I Th and Pa
    51. 51. Henry Moseley In 1913, through his work with X-rays, he determined the actual nuclear charge (atomic number) of the elements*. He rearranged the elements in order of increasing atomic number. *“There is in the atom a fundamental quantity which increases by regular steps as we pass from each element to the next. This quantity can only be the charge on the central positive nucleus.” His research was halted when the British government sent him to serve as a foot soldier in WWI. He was killed in the fighting in Gallipoli by a sniper’s bullet, at the age of 28. Because of this loss, the British government later restricted its scientists to noncombatant duties during WWII.
    52. 52. Glenn T. Seaborg After co-discovering 10 new elements, in 1944 he moved 14 elements out of the main body of the periodic table to their current location below the Lanthanide series. These became known as the Actinide series. 1912 - 1999
    53. 53. Glenn T. Seaborg He is the only person to have an element named after him while still alive. "This is the greatest honor ever bestowed upon me - even better, I think, than winning the Nobel Prize."
    54. 54. Thank you