Which of the following group `13` elements has the highest density?

Options

A. `Al`
B. `Ga`
C. `In`
D. `Tl`

Explanation

To determine which of the group 13 elements has the highest density, we can follow these steps:

### Step 1: Identify the Group 13 Elements
The group 13 elements include:
- Aluminium (Al)
- Gallium (Ga)
- Indium (In)
- Thallium (Tl)

### Step 2: Understand the Concept of Density
Density is defined as mass per unit volume (Density = Mass/Volume). As we move down a group in the periodic table, the atomic mass generally increases due to the addition of protons and neutrons.

### Step 3: Analyze the Trend of Density in Group 13
In group 13, the trend of density can be summarized as follows:
- Aluminium (Al) has a lower density compared to Gallium (Ga).
- Gallium (Ga) has a lower density than Indium (In).
- Indium (In) has a lower density than Thallium (Tl).

Thus, the order of density from lowest to highest is:
Al < Ga < In < Tl

### Step 4: Conclusion
Based on the trend observed, Thallium (Tl) has the highest density among the group 13 elements.

### Final Answer
**Thallium (Tl) has the highest density among the group 13 elements.**

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