The document discusses the development of the periodic table. It describes early classification systems by Dobereiner and Newlands that grouped elements based on properties but had limitations as new elements were discovered. Mendeleev organized the elements into the first recognizable periodic table based on atomic mass and predicted properties of undiscovered elements. Moseley later modified this to be based on atomic number. The modern periodic table is arranged into periods and groups with trends in properties like atomic radius, ionization potential, and electronegativity explained by variation in nuclear charge and number of electron shells across and down the table.

1. THE PERIODIC TABLE

2. IMPORTANCE OF
CLASSIFICATION
OF ELEMENTS
Organization and
relationship between
elements are defined.
Properties of elements can be
correlated with properties of
states of matter.

3. BASIS OF
CLASSIFICATION
OF ELEMENTS:
Early Chemists: based on
properties, valencies &
metallic and non-metallic
nature of elements.
The method was
discarded since elements
behave both as metals
and non-metals, shows
metallic and non-metallic
nature and have variable
valency.

4. DOBEREINER'S
LAW OF TRIADS :
• ’Chemically analogous elements arranged in increasing order of
atomic weights formed well marked groups of three called triads
in which the atomic weight of the middle element was found to
be generally the average of the atomic weights of the other two
elements.’

5. LIMITATIONS
OF
DOBEREINER’S
TRIADS:
The identification of new elements
made this model obsolete.
Newly discovered elements did not
fit into the triads.
Only a total of 5 Dobereiner’s
triads were identified.
Even several known elements did
not fit into any of the triads.

6. NEWLANDS LAW OF
OCTAVES:
• When the elements
are arranged in
increasing order of
their atomic masses,
the properties of the
eighth element are
like that of the first.

7. LIMITATIONS OF
NEWLANDS' LAW
OF OCTAVES:
• It was applicable to only lighter elements having
atomic masses up to 40, i.e., up to calcium. After
calcium, the first and the eighth element did not
have similar properties.
• It failed to leave spaces for undiscovered elements.

8. MENDELEEV’S
PERIODIC LAW:
• The Physical and Chemical Properties of the elements are
periodic functions of their atomic weights.

10. MENDELEEV’S CONTRIBUTIONS:
Elements were
arranged in
increasing order of
atomic weights in
periods and groups.
Elements with
similar chemical
properties are
grouped together.
Elements in the same
group had the same
valency.
Gaps were left for
undiscovered
elements.
The properties of the
undiscovered
elements were
predicted.
Incorrect atomic
weights of some of
the arranged
elements were
corrected.

11. DEFECTS IN
MENDELEEV’S
PERIODIC
TABLE:
Anomalous pairs – certain pairs of elements having
higher atomic weights have been given positions
before the elements having lower atomic weights
E.g. – Co – cobalt was placed before Ni - Nickle
Position of isotopes
Position of rare earths and actinides

12. MODERN PERIODIC LAW:
• Moseley modified Mendeleev’s periodic law to form the modern periodic law – The
physical and chemical properties of elements are the periodic function of their
atomic numbers.

13. PERIODICITY OF ELEMENTS
Gradual change in
properties is seen with
increase in atomic number
Periodicity – recurrence in
properties are seen in:-
Elements belonging to the
same subgroup
After a difference of 2,8,18
or 32 in atomic numbers
due to recurrence of similar
valence electronic
configuration.

14. SALIENT
FEATURES OF
MODERN
PERIODIC
TABLE
1. The modern periodic table has 7 horizontal rows called
'Period'.
Elements of the same period have the same number of electron
shells.
Electrons in the outermost shell increases progressively for
elements of the same period.
Period number signifies the number of electron shells.
Transition from metallic to non-metallic character.
Separation of elements : => Reactive metals: group IA and 2A
=>Transition metals: in the middle
=>Non - Metals: upper right corner

15. THERE ARE 18
VERTICAL
COLUMNS IN THE
PERIODIC TABLE
CALLED
‘GROUPS’.
• 2.There are 18 vertical columns in the periodic table called ‘Groups’.
• Group 1-alkali metals
• Group 2- alkaline earth metals
• Group 3- 12 – transition elements
• Group 13-16 – post transition elements
• Group 17 –halogens
• Group 18 – noble / inert gases.
• Group 1,2,13,14,15,16,17 – normal elements/representative elements.
• Group number signifies the number of valence electrons of an element.
• Elements of the same group have the same number of valence electrons
hence same valency and similar properties.
• Number of electron shells increases by one
• Metallic character increases down a group.

16. PERIOD IN A PERIODIC TABLE
In the periodic table of the elements, each numbered row is a period. In
the periodic table of the elements, elements are arranged in a series of rows
(or periods) so that those with similar properties appear in a column.
Number of electron shells remain the same from left to right of a period.
Valance electrons increases by one from left to right of a period.
The non - metallic character increases from left to right of a period.

17. BRIDGE
ELEMENTS
They show similarities in properties diagonally
with the period of the next group.

27. GROUP IN A PERIODIC TABLE
• A group (also known as a family) is a column of elements in the periodic table of the
chemical elements. There are 18 numbered groups in the periodic table, but the f-
block columns (between groups 2 and 3) are not numbered.

32. PROPERTY
TRENDS –
DOWN A SUB-
GROUP
Valence electrons – Remain same
Chemical properties - Remain
same
Metallic character/electro positive
character – increases down
No. of electron shells increases by
one.

35. Group IA elements Group VIIA elements
Elements Li, Na, K, rubidium,
caseium, francium
Fl, Cl, Br, I, astatine
Valency 1 valence eˉ => Univalent 7 valence eˉ => univalent
Nature Highly – reactive and
electropositive ; light & soft
metals – can be cut with a
knife
Highly – reactive and electronegative;
Non - metals – some are gaseous,
liquid and solid at room temp.
Conductivity Good Bad or Non - conductors
Reducing / oxi-
dizing agents
Strong reducing agents Strong oxidizing agents
Reaction with
Nonmetals
Electrovalent compounds are
formed
Covalent compounds are formed
Reaction with
‘H’
Ionic hydrides are formed Covalent hydrides are formed

36. PERIODICITY
Periodicity: occurrence of characteristic
properties of elements at definite intervals in
the modern periodic table when elements are
arranged in the increasing order of their
atomic numbers.
The cause of periodicity is the recurrence of
similar electronic configuration.

37. ATOMIC RADIUS/SIZE
• .
•Atomic radius: distance between the center of the nucleus
and the outermost shell. Unit => A°

38. FACTORS
AFFECTING
ATOMIC
RADIUS/SIZE
• Number of shells increases & atomic size increases
• Reason – As the No. of shells increases – the distance between the
nucleus and the outermost shell increases
• Nuclear charge increases and atomic size decreases
• Reason – Nuclear charge increases – the electrons of the
outermost shell are attracted with increasing force
• Nuclear charge is the positive charge of the atom
• Nuclear charge is equivalent to the atomic number of the element

39. TRENDS IN ATOMIC SIZE – FROM LEFT TO
RIGHT OF A PERIOD
• Number of shells – Remain the same and
Atomic Size – Remains unaffected
• Nuclear charge – Increases and Atomic size –
Decreases
• In Period 2 – Li – largest atomic Radius
• In period 2 – F - smallest atomic radius
• Neon has larger atomic radius as its
outermost shell is completely filled
• The effect of nuclear pull over the valence
shell electrons is not seen

40. TRENDS IN
ATOMIC SIZE;
DOWN A
GROUP
• Number of shells increases and atomic size
increases
• Nuclear charge increases and atomic size should
decrease
• Atomic radius/size increases down a group

41. IONIZATION POTENTIAL
• .
•Ionization potential : amount of energy required to remove an
electron from the outermost shell of an isolated gaseous atom.
Unit => eV

42. FACTORS
AFFECTING –
IONIZATION
POTENTIAL
• Atomic size increases and Ionization potential – Decreases
• Reason – Atomic size increases and the nuclear attraction on
the outer electron - decreases
• Outer electrons are loosely held
• Nuclear charge increases and ionization potential – increases
• Reason – Nuclear charge increases and the nuclear attraction
on the outer electron – increases
• Outer electrons are tightly held

43. TRENDS IN IONIZATION POTENTIAL
Helium has highest
ionization potential
while caesium has
the lowest
01
Metals lose electrons
and so have low I.P.
compared to non-
metals
02
I.P. increases across
a period
03

44. TRENDS IN I.P. – DOWN A GROUP
• Atomic radius increases and I.P. decreases
• Nuclear charge – Increases and so I.P. should decrease
• I.P. decreases down a group

45. ELECTRON
AFFINITY
• amount of energy released when an
atom in the gaseous state accepts an
electron to form an anion. Unit is eV

46. FACTORS
AFFECTING
ELECTRON
AFFINITY
• Atomic size increases and Electron affinity
decreases
• Reason: A small atom takes up electrons more
readily than a large atom
• Because the nucleus has greater attraction on the
electrons
• Nuclear charge increases and electron affinity
increases
• Nuclear charge increases:
• Similarly increases the tendency of atom to
accept electrons

47. TRENDS IN
ELECTRON
AFFINITY –
ACROSS A
PERIOD –
FROM LEFT –
RIGHT
• Atomic radius decreases and electron affinity increases
• Nuclear charge increases and electron affinity increases
• Neon has electron affinity zero as its outermost shells are filled
• Electron affinity is highest for halogens group 17 and least for
alkali metals group 1
• More value of electron affinity more is the electronegativity
• Electron affinity increases across a period from left to right

48. TRENDS IN
ELECTRON
AFFINITY
DOWN A
GROUP
• Atomic radius increases and E.A. decreases
• Nuclear charge – Increases and so E.A. should
decrease
• E.A. decreases down a group

49. ELECTRO -
NEGATIVITY
• It is the tendency of an atom to attract itself in the
gaseous state accepts an electron to form an anion

50. FACTORS
AFFECTING
ELECTRO-
NEGATIVITY
• Atomic size increases and electro-negativity decreases.
• Nuclear charge increases and electronegativity increases
• Reasons – same as electron affinity

51. TRENDS IN
ELECTRO-
NEGATIVITY
ACROSS A
PERIOD FROM
LEFT TO RIGHT
• Atomic radius decreases and electro-negativity increases
• Nuclear charge increases and electro-negativity increases
• Elements with high electronegativity are usually non-metallic
• Fluorine is the most electronegative element and caesium id the
least
• Noble gases have complete octet and so they do not attract
electrons
• electro-negativity increases across a period from left to right

52. TRENDS IN
ELECTRO-
NEGATIVITY
DOWN A GROUP
• Atomic radius increases and electro-negativity
decreases
• Nuclear charge increases and electro-negativity
should increase
• Electro-negativity decreases down a group

53. FEATURES OF LONG FORM OF PERIODIC
TABLE
1. 18 vertical columns known as groups.
2. 7 Horizontal rows known as periods.
3. Light metals These are elements of periodic table of group 1 and 2.
4. Heavy metals or Transition metals - These are elements of periodic
table of group 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12.
5. Non-Metals These are elements of periodic table of group 13, 14, 15,
16 and 17.
6. Zero group These are elements of periodic table of group 18.

54. METALLIC
AND NON -
METALLIC
CHARACTER -
TERM
Metallic character
electro positive
Non - Metallic
character
In terms of
electron losing
property – an atom
is said to be a –
Metal , if it loses
one or more
electrons when
supplied with
energy.
In terms of
electron gaining
property – an atom
is said to be a –
Metal , if it gains
one or more
electrons when
supplied with
energy.

55. FACTORS
AFFECTING
METALLIC
AND NON-
METALLIC
CHARACTER
Atomic radius increases and metallic character increases ,
nonmetallic character decreases.
I.P. increases and metallic character decreases , nonmetallic
character increases.
Metallic atoms are present on the left side of the periodic
table have large atomic radius and low I.P. value and lend to
lose – electrons
Non - Metallic atoms are present on the right side of the
periodic table have small atomic radius and high I.P. value
and lend to gain – electrons
Metals are good reducing agents
Non – Metals are good oxidizing agents

56. TRENDS IN CHARACTER – ACROSS A PERIOD
FROM LEFT TO RIGHT
• Atomic radius decreases and metallic character decreases ; non –
metallic character increases
• I.P. increases and metallic character decreases ; non – metallic
character increases
• Metallic character decreases across a period ; Non – metallic character
increases across a period

57. TRENDS A
CHARACTER
DOWN A
GROUP
Atomic radius increases and
metallic character increases ; non –
metallic character decreases
I.P. decreases and metallic
character increases ; non – metallic
character decreases
Metallic character increases across
a period ; Non – metallic character
decreases across a period

60. PHYSICAL PROPERTIES - DENSITY AND
MELTING POINT
Across a period – density
and & melting points –
increase gradually

61. PHYSICAL PROPERTIES - DENSITY AND
MELTING POINT AND BOILING POINT
Down a group density
increases gradually & m.p &
b.p. of elements decreases
gradually

62. CHEMICAL PROPERTIES – PERIODICITY IN
PROPERTIES OF COMPOUNDS OF ELEMENTS
Characteristics Varies across a period Varies down a group
Oxides Strongly basic to
strongly acidic
Acidic to Basic
Hydroxides Strongly basic to
Amphoteric
Less basic to Strongly
basic
Oxy-acids Weak oxy-acids to
Strong oxy-acids
Strong oxy-acids to
Weak oxy-acids
Hydrides Strongly basic to
strongly acidic
Less Acidic to More
Acidic

63. STABLE AND UNSTABLE ELEMENTS
Elements arranged in the periodic table having n/p
(neutrons/protons) ratio around 1 are stable
Elements arranged in the periodic table having n/p
(neutrons/protons) ratio above 1.5 are unstable stable
E.g. – light – Na ; heavy – uranium.

65. MODERN PERIODIC TABLE

66. ABOUT
• There are 18 vertical columns in the periodic
table. Each column is called a group. All elements
in a group have similar chemical and physical
properties because they have the same number of
outer electrons.
In periodic table elements are arranged in a series
of rows. Elements of the same period have the
same number of electron shells.

67. MODERN PERIODIC LAW
• The properties of elements are the periodic
function of their atomic number i.e. number of
protons.

68. POSITION OF ELEMENTS IN THE PERIODIC
TABLE

69. LOCATION OF
METALS, NON-
METALS,
METALLOIDS
AND NOBLE
GASES ARE AS
FOLLOWS:
Elements on the left and middle
are Metals
Elements on the right are Non-metals
Metalloids form the narrow stair-step
area between metals and non-metals
The last group (18) to the right
are Noble gases

70. PERIODIC TABLE CHART
• The Periodic Table organizes the elements
according to their similar chemical and physical
properties. The Table has rows and columns. The
vertical columns in the periodic table
represent Groups. The horizontal rows in table
represents Periods.

71. DETERMINE
THE PERIOD
NUMBER OF
ELEMENTS
• All the elements in a period have the same
number of atomic orbitals. For example, every
element in the top row (the first period) has one
orbital for its electrons. All the elements in the
second row (the second period) have two orbitals for
their electrons.

72. DETERMINE THE GROUP
NUMBER OF ELEMENTS
• The group number is an identifier used to describe
the column of the standard periodic table in which
the element appears. Groups 1-2 (except
hydrogen) and 13-18 are termed
main group elements. Groups 3-11 are termed
transition elements.
Electronic configuration of Sodium is 2, 8, 1. So
the number of group is 1

73. OCCURRENCE OF ALKALI EARTH METALS
• Alkaline earth metals are obtained in the form of their ore in earth's
crust. Of the alkaline earth metals calcium and magnesium rank fifth
and sixth in abundance respectively, in earth crust. Beryllium is rare
and radium is rarest of all.

74. CHARACTERISTICS
• Alkali metals are highly reactive elements. They are soft, have
low density, low melting point, low boiling point, give
characteristic color to the flame, are strongly electro-positive
character. They react with water liberating H2 and react with
acids replacing hydrogen.

75. NOBLE GASES
Noble gases are the gases
present in
group VIIIA(18) which has
its outer shell completely
fill. Some of the common
properties of noble gases
are:
Almost Non-reactive High ionization energies
Very low
electronegativities
Low boiling points (all
monatomic gases at room
temperature)
No color, odor, or flavor
under ordinary conditions
Non-flammable
At low pressure, they will
conduct electricity