Describe the main features of the long form of the periodic table. In what respects is it superior to Mendeleev's table ?

Explanation

### Step-by-Step Text Solution

**1. Introduction to the Long Form of the Periodic Table:**
- The long form of the periodic table, also known as the modern periodic table, was developed by Henry Moseley. It organizes elements based on their atomic number rather than atomic mass, which was the basis for Mendeleev's table.

**2. Structure of the Long Form:**
- The modern periodic table consists of **7 periods** (horizontal rows) and **18 groups** (vertical columns).
- The periods are categorized as follows:
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