The most effective projectile in the transmutation of heavy element is `……………….` .

Answer

To solve the question regarding the most effective projectile in the transmutation of heavy elements, we can follow these steps:

### Step 1: Understand the Concept of Transmutation
Transmutation refers to the process of changing one element into another through nuclear reactions. This can involve bombarding a nucleus with particles.

### Step 2: Identify the Types of Projectiles
The common projectiles used in nuclear reactions include:
- Alpha particles (α)
- Protons (p)
- Deuterons (d)
- Neutrons (n)

### Step 3: Analyze the Charge of Each Projectile
- **Alpha particles**: These are positively charged and can be repelled by the positively charged nucleus.
- **Protons**: Also positively charged, they experience similar repulsion from the nucleus.
- **Deuterons**: These are positively charged as well and will also be repelled by the nucleus.
- **Neutrons**: Neutrons are neutral particles and do not experience any electrostatic repulsion from the nucleus.

### Step 4: Determine the Most Effective Projectile
Since alpha particles, protons, and deuterons are all positively charged, they are repelled by the nucleus, making them less effective for transmutation. In contrast, neutrons, being neutral, can easily penetrate the nucleus without repulsion. Therefore, they are the most effective projectiles in the transmutation of heavy elements.

### Conclusion
The most effective projectile in the transmutation of heavy elements is **neutrons**.

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