Which group of elements was missing from Mendeleev's original periodic table ?

Explanation

**Step-by-Step Solution:**

1. **Understanding Mendeleev's Periodic Table**: Mendeleev's original periodic table was created in 1869 and was based on the atomic masses of elements. He arranged the elements in order of increasing atomic mass and grouped them according to similar chemical properties.

2. **Identifying the Groups**: Mendeleev's table included metals, nonmetals, and metalloids. However, it did not account for all known elements at the time, particularly those that had not yet been discovered.

3. **Recognizing the Missing Group**: The group that was notably absent from Mendeleev's original periodic table is the noble gases. Noble gases include helium, neon, argon, krypton, xenon, and radon. These elements were not discovered until after Mendeleev published his table.

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