Session Opener

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Session Opener
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Session Objectives

• Why do we need classification.?
• Dobereniners triads
• Newlands law of octave
• Lother Meyer volume curve
• Mendeleevs periodic table
• Modern periodic table
• IUPAC nomenculature for elements Z gt100

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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.
Lavoisier (1789) classified elements into metals,
non-metals, gases and earths.
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Dobereiners 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
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John Newlands
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.
Law of Octaves
1838 - 1898
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Newlands law of octaves John Newland (1862)
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Do you know?
Newland was first to publish the list of elements
in increasing order of atomic masses.
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Lother-Meyers atomic volume curve Lother Meyer
(1869)
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Illustrative Problem

• If elements A,B and Z occupy similar positions in
  Lother meyer curve, they will have----properties
• Different
• Similar
• Cannot say

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Mendeleevs periodic law
The physical and chemical properties of elements
are periodic function of their atomic masses.
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Mendeleevs periodic table
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Mendeleevs periodic table
Only 63 elements were known.
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.

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Merits of Mendeleevs periodic table
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Defects of Mendeleevs periodic table
Position of isotopes e.g. 1H1, 1H2, 1H3

• Anomalous pairs.(Ar and K, Co and Ni, Te and
  I)

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Defects of Mendeleevsperiodic table
Chemically dissimilar elements are grouped
together. (Cu-IA and Na-IB)
Chemically similar elements are placed in
different groups. Cu (I) and Hg (II).
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Illustrative Problem

• Mendeleev gave more importance to -----while
  arranging the elements in long form of periodic
  table
• atomic mass
• atomic volume
• atomic number
• similarity in property

Solution
Option (a) is correct.
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Do you know?
Mendeleevs periodic table was published in 1905
when no one had an idea of the structure of an
atom.
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Modern periodic law (Moseley)
The physical and chemical properties of elements
are periodic function of their atomic numbers.
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Modern periodic table
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Quiz
Write the electronic configuration of elements
having following atomic numbers. (a). 19
(b). 32 (c). 41 (d). 58
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s block elements

• Electronic configuration

ns1 or ns2

• Groups

IA and IIA

• Low ionisation energy and low melting and
  boiling points, electropositive elements.

• Colourless compounds.

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p block elements

• Electronic configuration

ns2,np1-6

• Groups

III A to VII A and zero group.

• Non-metals, electronegative.

• Form covalent compounds.

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d block elements

• Electronic configuration

(n-1)d1-10 ns1or2

• Groups

I B to VII B and VIII groups.

• Variable valency high melting and boiling point.

• Coloured compounds and catalytic property.

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f block elements

• Electronic configuration

(n-2)f1-14(n-1)d0-1ns2

• Present below the periodic table in two rows

• Lanthanides-elements after lanthanum

• Actinides-elements after actinium.

• Have high melting and boiling point.

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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.

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Features of long form of periodic table
Vertical column
Groups
Total 18. Numbered 1-18 orIA to VII A, IB to VII
B, VIII and zero.
Elements in a group have similar but
notidentical electronic configuration and
properties
Horizontal column
Periods
Total 7 numbered from 1 to 7.
Contains 2,8,8,18,18,32 and 28 elements
respectively.
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Features of long form of periodic table
Representative elements
s and p block elements .
Transition 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.
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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.

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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.

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Defects of long form of periodic table
It is unable to include lanthanides and
actinides in itsmain body.
The problem of the position of hydrogen in the
tablehas not beensolved completely
Configuration of Helium(1s2 ) is different
from inertgases (ns2,np6) but are placed in the
same group.
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Nomenclature of the elementswith atomic
numbergt100
Namedigits nameium
e.g. atomic number 115 will be named as
ununpentiumununpentium and symbol is Uup
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Class Exercise - 1
X, Y and Z are the elements of Dobereiners
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 Dobereiners law of
triads.
Hence, answer is (b).
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Class Exercise - 2
Newlands law of octave is appliedto all the
elements having atomicmass less than
______.(a) 20 (b) 40 (c) 30 (d) 10
Solution
From Newlands law of Octave.
Hence, answer is (b).
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Class Exercise - 3
Discovery of _________ isresponsible for failure
of lawof octave.(a) lanthanides (b)
actanides(c) transition elements (d) noble gases
Solution
From Newlands law of Octave.
Hence, answer is (d).
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Class Exercise - 4
Properties of element E are similar tothat of
element T. If element T ispresent on ascending
side of LotherMeyer graph, where will you
findelement E?(a) on descending side (b) on
peak(c) on ascending side (d) None of these
Solution
The elements having similar properties occupy
similarpositions on the Lother Meyer volume
curve.
Hence, answer is (c).
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Class Exercise - 5
How many elements were knowwhen Mendeleev
prepared hisperiodic table?(a) 53 (b) 63 (c)
51 (d) 76
Solution
Mendeleevs periodic table based on 63 elements.
Hence, answer is (b).
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Class Exercise - 6
The valence shell electronicconfiguration of an
element isRn 7s26d55f14. The elementbelongs
to(a) actinide series (b) lanthanide
series(c) 6d transition series (d) p block
Solution
Because last electron enters into d subshell
ofpenultimate orbit.
Hence, answer is (c).
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Class Exercise - 7
Which of the following groups havechemical
properties that are mostsimilar?(a) N, O,
S (b) Na, K, Rb(c) Na, Mg, Ca (d) Na, Rb, Mg
Solution
Because they belong to same group. (IA)
Hence, answer is (b).
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Class Exercise - 8
In which orbitals does thedifferentiating
electron enters in caseof inner transition
elements?(a) (n 1)d (b) ns1(c) ns2,
np16 (d) (n 2)f
Solution
f-block elements are known as inner-transitionele
ments.
Hence, answer is (d).
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Class Exercise - 9
Solution
Mass number number of proton number of
neutron 50 (112 50) 50 62 112
Hence, answer is (b).
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Class Exercise - 10
The name of element having atomicnumber 101
is(a) Rutherfordium (b) Lawrencium(c)
Hassium (d) Mendelevium
Solution
Rutherfordium 104 Lawrencium 103 Hassium 108
Hence, answer is (d).
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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?
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Dmitri Mendeleev
In 1869 he published a table of the elements
organized by increasing atomic mass.
1834 - 1907
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Lothar Meyer
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.

1830 - 1895
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Illustrative example
So why is Mendeleev called the father of the
modern periodic table and not Meyer, or both?
Solution

• 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.

After the discovery of these unknown elements
between 1874 and 1885, and the fact that
Mendeleevs predictions for Sc, Ga, and Ge were
amazingly close to the actual values, his table
was generally accepted.
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However, in spite of Mendeleevs 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
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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 snipers bullet, at the age of 28. Because
of this loss, the British government later
restricted its scientists to noncombatant duties
during WWII.
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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 knownas the
Actinide series.
1912 - 1999
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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, thanwinning the Nobel
Prize."
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