CLASS XII CHEMISTRY

PERIODS

Horizontal rows in the periodic table are called Periods.It is given by the quantum nuber of the outermost shell.

1st Period:

* It is the shortest period containing H and He.

2nd & 3rd Periods:

* Each contains eight elements and called the short period.

4th & 5th Periods:

* Each contains eighteen elements and called the long period. 

6th Period:

* It is the longest period that contains 32 elements.

7th Period:

* This is incomplete period.