Which transition metal has lowest density ?

Options

A. Sc
B. Ti
C. Zn
D. La

Answer

To determine which transition metal has the lowest density, we can follow these steps:

### Step 1: Understand Density
Density (ρ) is defined as mass (m) per unit volume (V):
\[ \rho = \frac{m}{V} \]
This means that density is influenced by both the mass of the atom and the volume it occupies.

**Hint:** Remember that density increases with mass and decreases with volume.

### Step 2: Identify the Metals
The transition metals mentioned in the question are Scandium (Sc), Ytterbium (Yb), and Lanthanum (La). We need to analyze their positions in the periodic table:
- Scandium (Sc) is in the 3d series.
- Ytterbium (Yb) is in the 4f series.
- Lanthanum (La) is in the 5d series.

**Hint:** Look at the periodic table to understand the groups and periods of the metals.

### Step 3: Analyze Trends in Density
As we move down a group in the periodic table:
- The atomic size (volume) generally increases due to the addition of electron shells.
- The mass also increases as more protons and neutrons are added.

However, the increase in mass tends to be more significant than the increase in volume, leading to an increase in density.

**Hint:** Consider how the atomic size and mass change as you go down a group.

### Step 4: Compare the Metals
- Scandium has a relatively low mass and a smaller volume compared to Lanthanum and Ytterbium.
- As we go from Scandium to Lanthanum, both mass and volume increase, but the increase in mass is more pronounced.

**Hint:** Think about how the mass and volume of each metal compares to one another.

### Step 5: Conclusion
From the analysis:
- Scandium has the lowest density among the three metals discussed because it has a lower mass compared to Lanthanum and Ytterbium, and its volume is not significantly larger to offset the lower mass.

Thus, the transition metal with the lowest density is **Scandium (Sc)**.

**Final Answer:** Scandium (Sc)