The vertical columns in Mendeleev's table were called :

Explanation

**Step-by-Step Solution:**

1. **Understanding Mendeleev's Table**: Mendeleev's periodic table is organized into periods and groups. The table consists of seven periods (horizontal rows) and eight groups (vertical columns).

2. **Identifying the Structure**: In Mendeleev's table, the vertical columns are referred to as groups. These groups contain elements that have similar chemical properties.

3. **Conclusion**: Therefore, the vertical columns in Mendeleev's table are called **groups**.

**Final Answer**: The vertical columns in Mendeleev's table were called **groups**.

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