Periodic properties

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Employee Opinion SurveyTo simplify and systematize the study of
chemistry of the elements and their
compounds, they are classified into
groups and periods.
NEED FOR CLASSIFICATION

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It was the first attempt towards
classification. He arranged similar elements
in a group of three elements called triad
and the atomic mass of the middle
elements of the traid is approximately the
arithmetic mean of the other two.
DOBEREINER’S LAW OF TRAIDS

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Employee Opinion SurveyWhen the lighter elements are arranged in
order of their increasing atomic weights,
then every eighth element is similar to the
first element in its properties, similarly as
the eighth node of a musical scale
is similar to 1st one.
NEWLAND’S LAW OF OCTAVES

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The graph plotting the atomic volumes
against atomicweights are known as
Lothar Mayer volumecurves
LOTHER MEYER ARRANGEMENT

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MENDELEEV’SPERIODIC LAW
The physical and chemical properties
of elements are periodic functions
of their atomic weight.

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DEMERITS OF MENDELEEV’S
PERIODIC TABLE
Position of hydrogen- Mendeleev could not
decide where to place it.
Position of isotopes- there were no places for
isotopes in Mendeleev’s table.
Anomalous pairs of elements- some pairs of
elements did not follow the increasing order
of atomic wts.
Like elements were placed in different groups.
Unlike elements were placed in same group.

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MODERN PERIODIC LAW
The properties of elements are the
periodic functions of their atomic
numbers

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FEATURES OF MODERN
PERIODIC LAW (1/2)
It consists of 18 vertial columns called
Groups and 7 horizontal rows called
Periods.
Elements of groups, 1, 2, 13 – 17 are called
normal or representative elements.
Elements of groups 3 – 11 are called
transition elements.

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FEATURES OF MODERN
PERIODIC LAW (2/2)
The 14 elements with atomic numbers (Z) = 58
– 71 are called lanthanides or rare earth
elements
The 14 elements with atomic numbers (Z) = 90
– 103 are called actinides.
The elements belonging to a particular group
are said to constitute a chemical family which
is usually named after the name of the first
element.

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DEFECTS OF MODERN
PERIODIC TABLE
The position of hydrogen is still disputable in
group IA as well as IVA & VIIA.
Helium being inert gas have
configuration different from that of the other
inert gas elements
Lanthanide and actinide series could not be
adjusted in themain periodic table and
therefore theyhad to be placed in a separate
block below the periodic table.

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CLASSIFICATION IN BLOCKS (1/2)
s-block elements- Elements of groups 1 and
2 including He in which the last electron
enters the s-orbital of the valence shell are
called s-block elements
p-block elements- Elements of groups 13–18
in which the last electron enters the p-
orbitals of the valence shell are called
p-block elements.

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CLASSIFICATION IN BLOCKS (2/2)
d-block elements- These are the elements of
Group 3 to 12 which are characterised by the
filling of inner d orbitals
by electrons and are therefore referred to
as d-block elements
f- block elements- In these elements, the f-
subshell of the anti-penultimate is being
progressively filled up. There are two series of
f-block elements each containing 14
elements.

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TEMPORARY NOMENCLATURE
The IUPACproposed a systemfor naming
elementswith Z> 100.
The names are derived byusing roots for the
three digits in the atomic number of the
elements and adding the ending -ium.The
roots for the numbers are

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EFFECTIVE NUCLEAR CHARGE
The effective nuclear charge is the net
charge an electron experiences in an atom
with multiple electrons.
The effective nuclear charge may be
approximated by the equation:

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PERIODIC PROPERTIES (1/4)
Properties which are directly or indirectly
related to their electronic configuration and
show a regular gradation when we move
from left to right in a period or from top to
bottom in a group are called periodic
properties

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1. Atomic Radius- An estimate of the atomic
size can be made by knowing the distance
between the atoms in the combined state.
i. Covalent radius- It is defined as one-half of
the distance between the nuclei of two
covalently bonded atoms of the same
element in a molecule.

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ii. Van derWaals’radius-It is defined as one-half
of the distance between the nuclei of two
non-bonded isolated atomsor two adjacent
atomsbelonging to two neighbouring
molecules of an element in the solid
state.

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2. Ionic Radius- The ionic radii can be
estimated by measuring the distances between
cations and anions in ionic crystals.
- Isoelectronic species- Atoms and ions which
contain the same number of electrons are
called isoelectronic species.

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IONISATION ENTHALPY
The energy required to remove an electron
from an isolated gaseous atom species (X) in
its ground state is called Ionisation enthalpy.
Itis expressed in units of kJ mol–1.
The value of Ionisation potential normally
increases on going from left to right in a
period and ionisation potential normally
decreases on going from top to bottom in a
group.

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FACTORS AFFECTING IONISATION
POTENTIAL (1/2)
- Atomic size:
- Effective nuclear charge:
- Shielding effect:

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FACTORS AFFECTING IONISATION
POTENTIAL (2/2)
- Stability of half filled and fully filled orbitals:
The atoms whose orbitals are half-filled or
fully-filled have greater stability than the
others.
- Penetration power:

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ELECTRON GAIN ENTHALPY
The enthalpy change accompanying the
process of adding up one mole of electron to
one mole of neutral atom(A) in its gaseous
state to form an anion (A–) is defined as
electron gain enthalpy/electron affinity of
that atom.
The values of electron affinity normally
decreases on going from top to bottom in a
group and Increases on going from left to
right in a period

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FACTORS AFFECTING ELECTRON
GAIN ENTHALPY (1/2)
- Effective Nuclear charge:
- Atomic Size orAtomic Radius:
- Shielding effect:

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FACTORS AFFECTING ELECTRON
GAIN ENTHALPY (2/2)
- Stability of Fully-Filled and Half-Filled Orbitals:
The stability of the configuration having fully-
filled orbitals and half-filled orbital is relatively
higher than that of other configurations.

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ELECTRONEGATIVITY
The measure of the capacity or tendency of
an atom to attract the shared pair of
electrons of the covalent bond towards itself
is called electronegativity of that atom.
Electronegativity generally increases across a
period from left to right and decrease down
a group in the periodic table.

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FACTORS
AFFECTING ELECTRONEGATIVITY
- Atomic size:
- Effective Nuclear charge:
- Screening Effect: Increase in number of inner
electrons tends to decrease the
electronegativity due to screening effect.

Periodic properties

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Periodic properties