The charge to mass ratio of `alpha-` particles is approximately to the charge to mass ratio of protons:

Options

A. six times
B. four times
C. half
D. two times

Explanation

To solve the problem of comparing the charge to mass ratio of alpha particles to that of protons, we can follow these steps:

### Step 1: Understand the Charge and Mass of Alpha Particles and Protons
- **Alpha Particle (α)**: An alpha particle consists of 2 protons and 2 neutrons. Therefore, its charge (Q) is:
\[ Q_{\alpha} = 2e \]
where \( e \) is the elementary charge (approximately \( 1.6 \times 10^{-19} \) coulombs).

The mass (m) of an alpha particle is:
\[ m_{\alpha} = 4m_p \]
where \( m_p \) is the mass of a proton (approximately \( 1.67 \times 10^{-27} \) kg).

- **Proton (p)**: The charge (Q) of a proton is:
\[ Q_p = e \]
The mass (m) of a proton is:
\[ m_p = m_p \]

### Step 2: Calculate the Charge to Mass Ratio for Alpha Particles and Protons
- For the alpha particle, the charge to mass ratio (\( \frac{Q}{m} \)) is:
\[ \frac{Q_{\alpha}}{m_{\alpha}} = \frac{2e}{4m_p} = \frac{2}{4} \cdot \frac{e}{m_p} = \frac{1}{2} \cdot \frac{e}{m_p} \]

- For the proton, the charge to mass ratio is:
\[ \frac{Q_p}{m_p} = \frac{e}{m_p} \]

### Step 3: Compare the Ratios
From the calculations:
- The charge to mass ratio of the alpha particle is:
\[ \frac{Q_{\alpha}}{m_{\alpha}} = \frac{1}{2} \cdot \frac{e}{m_p} \]
- The charge to mass ratio of the proton is:
\[ \frac{Q_p}{m_p} = \frac{e}{m_p} \]

### Conclusion
Thus, we can conclude that:
\[ \frac{Q_{\alpha}}{m_{\alpha}} = \frac{1}{2} \cdot \frac{Q_p}{m_p} \]
This means that the charge to mass ratio of alpha particles is approximately half that of protons.

### Final Answer
The charge to mass ratio of alpha particles is approximately half that of protons.

---