What was Dobereiner's basis of classifying elements?

Explanation

**Step-by-Step Solution:**

1. **Introduction to Dobereiner's Classification:**
- Dobereiner, a German chemist, proposed a method for classifying elements based on their properties. His classification is known as the "triad" system.

2. **Definition of Triads:**
- A triad consists of three elements that exhibit similar physical and chemical properties. Dobereiner observed that certain groups of three elements could be categorized together due to their similarities.

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