Out of the following , which one is not emitted by a natural radioactive substance ?

Options

A. Electrons
B. Electronmagnetic radiations
C. Helium nuclei with charge equal to that of two protons
D. Neutrons

Answer

To solve the question of which particle is not emitted by a natural radioactive substance, we can follow these steps:

### Step 1: Identify the types of particles emitted during radioactive decay.
In natural radioactive decay, three types of particles are commonly emitted:
1. **Alpha particles** (α): These are helium nuclei, consisting of 2 protons and 2 neutrons, and carry a +2 charge.
2. **Beta particles** (β): These are high-energy, high-speed electrons or positrons emitted when a neutron in the nucleus converts into a proton.
3. **Gamma rays** (γ): These are electromagnetic radiation emitted from the nucleus during radioactive decay, usually following alpha or beta decay.

### Step 2: Analyze the options provided in the question.
The options given are:
1. Electrons
2. Electromagnetic radiations
3. Helium nuclei
4. Neutrons

### Step 3: Match the options with the particles emitted in radioactive decay.
- **Electrons**: This corresponds to beta particles, which are indeed emitted during radioactive decay.
- **Electromagnetic radiations**: This corresponds to gamma rays, which are also emitted during radioactive decay.
- **Helium nuclei**: This corresponds to alpha particles, which are emitted during radioactive decay.
- **Neutrons**: Neutrons are not emitted during radioactive decay; they are constituents of the nucleus and are not released as decay products.

### Step 4: Conclusion
Based on the analysis, the particle that is not emitted by a natural radioactive substance is **neutrons**. Therefore, the correct answer is option D: **neutrons**.

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