The atomic radius of Nb is closest to :

Options

A. Ta
B. Zr
C. Ni
D. Ag

Explanation

To determine the atomic radius of niobium (Nb) and identify which element has a radius closest to it, we can follow these steps:

### Step 1: Identify the Position of Niobium in the Periodic Table
Niobium (Nb) is located in the 5th period and the 5th group of the periodic table.

### Step 2: Identify Nearby Elements
The elements adjacent to niobium in the periodic table are:
- To the left: Zirconium (Zr)
- To the right: Tantalum (Ta)

### Step 3: Understand Trends in Atomic Radius
As we move from left to right across a period in the periodic table, the atomic radius generally decreases due to the increasing nuclear charge, which pulls the electrons closer to the nucleus. Conversely, as we move down a group, the atomic radius increases due to the addition of electron shells.

### Step 4: Compare Atomic Radii of Nearby Elements
- **Zirconium (Zr)**: Being to the left of niobium, zirconium will have a larger atomic radius than niobium.
- **Tantalum (Ta)**: Being to the right of niobium, tantalum will have a smaller atomic radius than niobium, but it is in the same group (5th group) and is directly below niobium in the periodic table.

### Step 5: Consider Lanthanide Contraction
Tantalum is affected by lanthanide contraction, which occurs due to the filling of the f-block elements. This contraction leads to a smaller atomic radius than expected for elements in the same group. Therefore, the atomic radius of tantalum is closer to that of niobium than that of zirconium.

### Step 6: Conclusion
Based on the trends and the effect of lanthanide contraction, we conclude that the atomic radius of niobium is closest to that of tantalum (Ta).

### Final Answer
The atomic radius of Nb is closest to Tantalum (Ta).

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