Why did Mendeleev leave some gaps in his Periodic Table?

Explanation

**Step-by-Step Solution:**

1. **Understanding Mendeleev's Periodic Table**: Mendeleev created the first widely recognized periodic table, organizing elements based on their atomic mass and chemical properties.

2. **Observation of Gaps**: While arranging the elements, Mendeleev noticed that certain elements had similar properties and should be grouped together. However, he found that some properties did not align perfectly with the existing elements.

3. **Prediction of Undiscovered Elements**: Mendeleev predicted that there were elements yet to be discovered that would fit into these gaps. For instance, he predicted an element he called "Eka-Silicon," which he believed would have properties similar to silicon.

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