To determine which unipositive ion possesses all three subatomic particles (electrons, protons, and neutrons), we need to analyze the options provided: Helium and Deuterium.
### Step-by-Step Solution:
1. **Understanding Unipositive Ions**:
- A unipositive ion is an ion that has lost one electron, resulting in a charge of +1. This means it has one less electron than the number of protons.
2. **Analyzing Helium (He)**:
- The atomic number of Helium (He) is 2, which means it has 2 protons.
- The mass number of Helium is 4, which means it has a total of 4 nucleons (protons + neutrons).
- To find the number of neutrons:
\[
\text{Number of Neutrons} = \text{Mass Number} - \text{Number of Protons} = 4 - 2 = 2
\]
- Therefore, a neutral Helium atom has 2 protons, 2 neutrons, and 2 electrons.
- When it becomes a unipositive ion (He⁺), it loses one electron, resulting in:
- Protons: 2
- Neutrons: 2
- Electrons: 1
- Thus, He⁺ has all three subatomic particles.
3. **Analyzing Deuterium (D)**:
- Deuterium is an isotope of Hydrogen, represented as \( ^2H \) or \( D \).
- The atomic number of Deuterium is 1, meaning it has 1 proton.
- The mass number of Deuterium is 2, which means it has a total of 2 nucleons.
- To find the number of neutrons:
\[
\text{Number of Neutrons} = \text{Mass Number} - \text{Number of Protons} = 2 - 1 = 1
\]
- A neutral Deuterium atom has 1 proton, 1 neutron, and 1 electron.
- When it becomes a unipositive ion (D⁺), it loses one electron, resulting in:
- Protons: 1
- Neutrons: 1
- Electrons: 0
- Thus, D⁺ does not have all three subatomic particles since it has no electrons.
4. **Conclusion**:
- Among the given options, the unipositive ion that possesses all three subatomic particles is Helium (He⁺).
### Final Answer:
The unipositive ion that possesses all three subatomic particles is **Helium (He⁺)**.
