Mendeleev was a Russian chemist, who contributed the most for the development of periodic table of elements wherein the elements were arranged on the basis of their fundamental property, the atomic mass and also on the similarity of chemical properties. Only 63 elements were known at his time. He arranged the 63 elements in the increasing order of their atomic masses and found that there was a periodic recurrence of elements with similar physical and chemical properties, He observed that elements with similar properties fall in the same vertical column. These vertical columns are called groups and horizontal rows of elements are called periods. Mendeleev predicted the existence of certain elements not known at that time and named two of them as Eka-silicon and Eka-aluminium.
Eka aluminium and eka silicon were later replaced respectively as :

Options

A. Germanium and gallium
B. Gallium and scandium
C. Gallium and germanium
D. Germanium and scandium

Explanation

To solve the question regarding the elements Eka-aluminium and Eka-silicon predicted by Mendeleev, we will follow these steps:

### Step 1: Understand Mendeleev's Predictions
Mendeleev, while creating his periodic table, predicted the existence of certain elements that had not yet been discovered. He named these hypothetical elements based on their position in the periodic table.

### Step 2: Identify the Elements
The elements predicted by Mendeleev were:
- **Eka-aluminium**: This was predicted to be an element that would have properties similar to aluminium.
- **Eka-silicon**: This was predicted to be an element that would have properties similar to silicon.

### Step 3: Discover the Actual Elements
After Mendeleev's time, scientists discovered the elements that corresponded to these predictions:
- **Eka-aluminium** was later discovered and named **Gallium (Ga)**.
- **Eka-silicon** was later discovered and named **Germanium (Ge)**.

### Step 4: Conclusion
Thus, the elements that replaced Eka-aluminium and Eka-silicon are:
- **Eka-aluminium** → **Gallium (Ga)**
- **Eka-silicon** → **Germanium (Ge)**

### Final Answer
Eka-aluminium was replaced by Gallium and Eka-silicon was replaced by Germanium.

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