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2. Periodic Classification Of Elements
The Modern PeriodicTable

4. ✓ The Modern PeriodicTable was introduced by Henry
Moseley
✓ During his time 92 elements were already
discovered.
✓ Based on his X-ray study analysis , he concluded that

5. • Elements should be arranged based on their Atomic
Number but not Atomic Mass
• Therefore all the 92 elements were arranged in
increasing order of their atomic number.
• There were
• 18 groups (Vertical column)
• 7 periods ( Horizontal row)

6. Group 1- 12 – Metals
Group 13-18 – Non Metals
B,Si,Ge,As,Sb,Te,Po – Metalloids

7. • The elements present in one single group will all have
same physical and chemical properties
• Elements present in the same group will have same
number of valence electrons.
• Periodicity – Elements shows similar physical and
chemical properties after certain gap is called as
Periodicity .

8. Modern Periodic Law states that, "Properties of the
elements are the periodic function of their atomic
number”

9. Position of Elements in Modern PeriodicTable
PeriodicTable has 18 vertical
Columns called as GROUPS and 7
horizontal Rows called as PERIODS
Importance of Group Number
• Elements present in the same group will
have same number of valence electrons
• For example- Group 1 will have 1
valence electrons
• Group 2 will have 2 valence electrons
• And so on

11. Importance of Period Number
Period number tells about the shell
number present in last number of
electrons
Therefore groups signifies an outer shell
electronic configuration
Also number of shell increases as we go
down the group

12. The number of elements in periods are
based on how electrons are filled in
various shells
The maximum number of electrons
that can be accommodated in a shell
depends on the formula 2n2 where n –
number of given shell from the nucleus

13. For example
K shell- 2× (1)2= 2 first period has 2
elements
L shell- 2× (2)2= 8 second period has 8
elements
3rd ,4th,5th ,6th ,7th period will
have 8,18,18,32,32 elements

14. The position of element in the periodic
table tells about the Chemical Reactivity
Valence Electrons determine the kind and
number of bonds formed by an element.

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