Which one of the following given d-block elements has the lowest atomic radii?

Options

A. Cu
B. Ti
C. Sc
D. Co

Answer

To determine which of the given d-block elements has the lowest atomic radii, we can follow these steps:

### Step 1: Identify the d-block elements
The d-block elements include transition metals, which are found in groups 3 to 12 of the periodic table. The elements mentioned in the question are:
- Copper (Cu)
- Titanium (Ti)
- Scandium (Sc)
- Cobalt (Co)

### Step 2: Understand the trend in atomic radii
In general, atomic radii decrease across a period from left to right due to the increase in nuclear charge, which pulls the electrons closer to the nucleus. However, within the d-block elements, the trend can be slightly different:
- Atomic radii generally decrease from Scandium (Sc) to Zinc (Zn) across the transition series.
- After reaching a minimum, the atomic radii may increase again due to electron-electron repulsion in the d-orbitals.

### Step 3: Compare the atomic radii of the given elements
From the periodic table and the trends in atomic radii:
- Scandium (Sc) has a larger atomic radius compared to Titanium (Ti).
- Titanium (Ti) has a larger atomic radius compared to Cobalt (Co).
- Cobalt (Co) has a larger atomic radius compared to Copper (Cu).

### Step 4: Determine the element with the lowest atomic radius
Based on the trends:
- Scandium (Sc) > Titanium (Ti) > Cobalt (Co) > Copper (Cu)

Thus, among the given elements, **Cobalt (Co)** has the lowest atomic radius.

### Conclusion
The d-block element with the lowest atomic radius among the given options is **Cobalt (Co)**.