How many periods are there in long form of periodic table?A: 6 B: 7C: 8D: 9

The long form of the periodic table consists of 7 periods. Here's a breakdown of how the periodic table is organized and what constitutes a "period":

Explanation:
Definition of Period:

A period in the periodic table is a horizontal row of elements. Each period corresponds to the principal quantum number (n) of the outermost electrons in the atoms of the elements in that row.
Long Form of the Periodic Table:

In the long form, elements are arranged in rows (periods) and columns (groups) based on their atomic number, electron configuration, and recurring chemical properties.
The elements in each period show a gradual change in properties from left to right.
Number of Periods:

The long form of the periodic table has 7 periods:
Period 1: Contains 2 elements (Hydrogen and Helium).
Period 2: Contains 8 elements (from Lithium to Neon).
Period 3: Contains 8 elements (from Sodium to Argon).
Period 4: Contains 18 elements (from Potassium to Krypton).
Period 5: Contains 18 elements (from Rubidium to Xenon).
Period 6: Contains 32 elements (from Cesium to Radon, including the Lanthanide series).
Period 7: Contains 32 elements (from Francium to Oganesson, including the Actinide series).
Conclusion:
Thus, the correct answer to the question is B: 7.