chemistry class 09 chapter 03 topic: periodic law and modren periodic table

1. CHEMISTRY 9
CHAPTER # 03
TOPIC:
PERIODIC LAW
AND
MODREN PERIODIC TABLE

2. PERIODIC LAW

3. In 1913 H. Moseley discovered a new
property of the elements that was
atomic number.

4. Atomic number is a more fundamental
property because
• atomic number of every element is
fixed.
• It increases regularly by 1 from
element to element.
• atomic number provides the basis of
electronic configurations

5. PERIODIC LAW
"properties of the elements are
periodic function of their atomic
numbers"

6. In 1913 Moseley gives a new
direction to the Mendeleev’s
periodic table which is now known
as modern periodic table.

7. MODREN PERIODIC
TABLE

8. The modern periodic table is based
upon the arrangement of elements
according to increasing atomic
number.

9. When the elements are arranged
according to increasing atomic number
from left to right in a horizontal row,
properties of elements were found
repeating after regular intervals It was
observed that after every eighth
element, ninth element had similar
properties to the first element

10. For example, sodium (Z=ll) had
similar properties to lithium (Z=3).
After atomic number 18, every
nineteenth element was showing
similar behaviour.

12. PERIODS
The horizontal rows of elements in
the periodic table are called periods.
• The elements in a period have
continuously increasing atomic
number

13. GROUPS
The vertical columns in the periodic
table are called groups.
• These groups are numbered from
left to right as 1 to 18.
• The elements in a group do not
have continuously increasing
atomic numbers.