APT ACADEMIC SOLUTIONS …apt way of teaching : APT ACADEMIC SOLUTIONS …apt way of teaching AAS believes in people who deliver the right solutions, and it proudly possesses them.
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Slide 3 : Periodic Table I
Session Objectives : Why do we need classification.?
Dobereniner’s triads
Newlands law of octave
Lother Meyer volume curve
Mendeleev’s periodic table
Modern periodic table
IUPAC nomenculature for elements Z >100 Session Objectives
Do you know : Lavoisier (1789) classified elements into metals, non-metals, gases and earths. Do you know
Doebereiner’s triads : Doebereiner’s triads In 1829, he classified elements into groups of three, which he called triads.The elements in a triad had similar chemical properties and orderly physical properties.
Illustrative example : Illustrative example 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. Hence, answer is (b).
John Newlands : John Newlands The English scientist John Newlands (1837-1898) arranged elements in groups of eight, but 'Newland's octaves', as they were called, were largely ignored by scientists.
Newland’s law of octaves [John Newland (1862)] : Newland’s law of octaves [John Newland (1862)]
Illustrative example : Illustrative example Newland’s law of octave is appliedto all the elements having atomicmass less than ______.(a) 20 (b) 40 (c) 30 (d) 10 Solution: Hence, answer is (b). Newland’s law of Octave cannot be applied to elements with atomic number greater than 20.
Illustrative example : Illustrative example Discovery of _________ isresponsible for failure of lawof octave.(a) lanthanides (b) actanides(c) transition elements (d) noble gases Hence, answer is (d). Discovery of noble gases was a failure of Newland’s law of Octave. Solution:
Do you know? : Newland was first to publish the list of elements in increasing order of atomic masses. Do you know?
Lother-Meyer’s atomic volume curve [Lother Meyer (1869)] : Lother-Meyer’s atomic volume curve [Lother Meyer (1869)]
Illustrative example : Illustrative example 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 similarpositions on the Lother Meyer volume curve. Hence, answer is (c).
Illustrative Problem : If elements A,B and Z occupy similar positions in Lother meyer curve, they will have----properties
Different
Similar
Cannot say Illustrative Problem
Mendeleev’s periodic law : Mendeleev’s periodic law 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. "...if all the elements be arranged in order of their atomic weights a periodic repetition of properties is obtained." - Mendeleyev The modern table was devised in 1869 by Dmitri Mendeleev
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Merits of Mendeleev’s periodic table : Merits of Mendeleev’s periodic table Prediction of new elements (Ge, Ga, Sc).
Systematic study of elements.
Correction of atomic mass (Be, Au, Pt).
Defects of Mendeleev’s periodic table : 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
Chemically dissimilar elements are grouped together. (Cu-IA and Na-IB)
Chemically similar elements are placed in different groups. [Cu (I) and Hg (II)].
Illustrative example : Illustrative example How many elements were known when Mendeleev prepared his periodic table?(a) 53 (b) 63 (c) 51 (d) 76 Hence, answer is (b). Mendeleev’s periodic table was based on 63 elements. Solution:
Do you know? : Mendeleev’s periodic table was published in 1905 when no one had an idea of the structure of an atom. Do you know?
Modern periodic law (Moseley) : Modern periodic law (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.”
Modern periodic table : Modern periodic table The physical and chemical properties of elements are periodic function of their atomic numbers.
s block elements : 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
p block elements : Electronic configuration: Groups: Non-metals, electronegative. Form covalent compounds. p block elements ns2,np1-6 III A to VII A and zero group.
d block elements : 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.
f block elements : Electronic configuration: Have high melting and boiling point. f block elements (n-2)f1-14(n-1)d0-1ns2 Present below the periodic table in two rows Lanthanides-elements after lanthanum Actinides-elements after actinium.
Illustrative example : Illustrative example 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-transitionelements.
Illustrative example : Illustrative example 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)
Features of long form of periodic table : 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.
Features of long form of periodic table : Features of long form of periodic table Groups Vertical column Total 18. Numbered 1-18 orIA 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 notidentical electronic configuration and properties Contains 2,8,8,18,18,32 and 28 elements respectively.
Features of long form of periodic table : Representative elements Transition elements s and p block elements . d block elements. Valence shell and penultimate shellboth are incomplete. Inner Transition elements f block elements. Valence shell, penultimate shell antipenultimate shell are incomplete. Features of long form of periodic table
Features of long form of periodic table : 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
Merits of long form of periodic table : 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
Defects of long form of periodic table : Defects of long form of periodic table The problem of the position of hydrogen in the tablehas not been solved completely.
Configuration of Helium(1s2 ) is different from inertgases (ns2,np6) but are placed in the same group.
It is unable to include lanthanides and actinides in itsmain body.
Illustrative example : Illustrative example Atomic number of element is 108. This element is placed in ____ block of periodic table.(a) s (b) p (c) d (d) f Hence, answer is (c). Atomic number — 108 Configuration — 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10,4p6, 5s2, 4d10, 5p6, 6s2, 4f14, 5d10, 6p6, 7s2, 5f14, 6d6
Illustrative example : Illustrative example The electronic configuration of an element is (n – 1)d1, ns2 where n = 4. The element belongs to ____ period of periodic table.(a) 3 (b) 2 (c) 5 (d) 4 Hence, answer is (d). The period number is same as maximum value of principalquantum number.
Illustrative example : Illustrative example The valence shell electronic configuration of an element is[Rn] 7s26d55f14. 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 ofpenultimate orbit.
Illustrative example : Illustrative example A, B, C and D have following electronicconfigurationsA : 1s2, 2s2, 2p1B : 1s2, 2s2, 2p6, 3s2, 3p1C : 1s2, 2s2, 2p6, 3s2, 3p4D : 1s2, 12s2, 2p6, 3s2, 3p6, 4s1Find out the periods of A, B, C and D. Hence, answer is (b). Period number is equal to maximum value of principal quantum number. Element A — 2nd period
Element B — 3rd period
Element C — 3rd period
Element D — 4th period
Nomenclature of the elementswith atomic number>100 : 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 elementswith atomic number>100
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