periodic law and modren periodic table

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.

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

12. 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.