What are horizontal rows and vertical columns of the periodic table called ?

Explanation

To answer the question about the horizontal rows and vertical columns of the periodic table, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Structure of the Periodic Table**:
- The periodic table is organized in a specific way to categorize elements based on their properties.

2. **Identifying Horizontal Rows**:
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