Metallic radii of some transition elements are given below. Which of these elements will have highest density ?
`{:("Element " ,Fe,Co,Ni,Cu),("Metallic radii/pm",126,125,125,128):}`

Options

A. Fe
B. Ni
C. Co
D. Cu

Explanation

To determine which of the given transition elements has the highest density, we can follow these steps:

### Step 1: Understand the relationship between density, mass, and volume
Density (\(D\)) is defined as mass (\(m\)) per unit volume (\(V\)):
\[ D = \frac{m}{V} \]
From this relationship, we can see that density increases with an increase in mass and a decrease in volume.

### Step 2: Analyze the given data
We have the following elements and their corresponding metallic radii:
- Iron (Fe): 126 pm
- Cobalt (Co): 125 pm
- Nickel (Ni): 125 pm
- Copper (Cu): 128 pm

### Step 3: Consider the trend in metallic radius and atomic mass
As we move from left to right in the periodic table:
- The atomic mass generally increases.
- The metallic radius generally decreases.

This means that for the elements listed, as we move from Iron to Copper, the atomic mass increases while the metallic radius (which is related to volume) decreases.

### Step 4: Compare the densities of the elements
To determine which element has the highest density, we need to consider both the atomic mass and the metallic radius. The density will increase if the atomic mass increases more significantly than the volume (related to the metallic radius) decreases.

The approximate densities of the elements are:
- Iron (Fe): 7.87 g/cm³
- Cobalt (Co): 8.90 g/cm³
- Nickel (Ni): 8.91 g/cm³
- Copper (Cu): 8.95 g/cm³

### Step 5: Identify the element with the highest density
From the densities listed, we can see:
- Copper has the highest density at 8.95 g/cm³.

### Conclusion
Thus, the element with the highest density among the given options is **Copper (Cu)**.