The presentation "Properties of Periodic Table" is prepared for grade IX students. The slide show includes a brief description on the properties of elements in the periodic table, that shifts periodically, hence explaining the concept of periodicity. the main topics include Atomic Radii, Ionization energy, Electron affinity and Electronegativity.
4. Atomic radii
Modern research shows that an atom
does not have strictly defined
boundaries. So it is impossible to
determine the exact radius of an atom.
5. “The atomic radius may be
defined as half the distance
between two adjacent nuclei of
two similar atoms in touch with
each other.”
6. Unit of atomic radii
It is measured in Angstrom.
Unit (Ao or A.U)
1Ao = 10-8 cm.
7. Factors on which atomic radii
depends
The atomic radii depends upon
1. The number of shells
2. And nuclear charge of an atom.
8. Atomic radii in groups
In the periodic
table the atomic
radii increase
down the group,
due to addition
of new shell in
each atom.
9. Atomic radii in periods
In a period the atomic radii decrease from left
to right due to increase in number of proton
that is increase in nuclear charge, which
results in stronger pull on orbiting electrons
by the nucleus.
11. “Ionization energy is the
minimum energy required to
remove an electron from a
gaseous atom in its ground
state.”
12. Unit of ionization energy
It is measured in K.Joles/mole or
electron volt (ev) per atom.
13. Factors on which ionization
energy depends
Ionization energy depends upon:
1. Atomic size
2. Nuclear charge.
14. The higher the ionization energy of an
atom, the more difficult is to remove
an electron.
The ionization energy of hydrogen is
1312 K.J/mol.
H(g) + Energy H+ + e-
I.E =1312KJ/mol
15. Ionization energy in Group
Down a group in
periodic table, the
ionization energy
decreases
because of
addition of a new
shell decreases
the hold of
nucleus on
valence electron.
16. Ionization energy in Periods
Ionization energy increases from left to
right in a period, because the addition of
proton in the nucleus, increase the
nuclear charge, thereby increasing the
force of attraction on electrons.
17. First ionization energy
The amount of energy required to
remove first electron is called first
ionization energy. For subsequent
electrons it is called second, third and
fourth ionization energy.
20. “Electron Affinity is defined as the
energy change that occurs when
an electron is gained by an atom
in the gaseous state.”
21.
22. Unit of Electron Affinity
It is measured in KJ/mol or in ev per
atom
23. Electron affinity for the first atom is
negative, i.e. Energy is released but
for further addition of electrons it is
positive, because energy has to be
added to overcome repulsion between
negative ions and electrons.
24. Electron Affinity of Fluorine
Fluorine have very small electron
affinity because due to its very small
atomic size it does not accept electron
easily.
25. Electron Affinity
in Group Down the group
in periodic table
Electron Affinity
decreases
because of the
addition of new
shell to each
atom
decreases its
force of
attraction.
26. Electron
Affinity in
Period
In period the
electron
affinity
increases
from left to
right,
because
successive
atoms have
higher
nuclear
charge and
attract the
incoming
electrons
more towards
itself.
31. Linus Pauling calculated the
electronegativity of different elements
taking fluorine as standard with its
electronegativity=4.
32. Electronegativity in Group
Down the group ----- Electronegativity
decrease.
Due to addition of new shells, the power of a
nucleus to attract new electrons decreases.
33. Electronegativity in Period
In period from left to right ----
electronegativity increase due to
increase in nuclear charge.
