When an `alpha`-particle is emitted

Options

A. element moves 2 places to the right in the periodic table
B. element moves one place to the left
C. element moves 2 places to the left in the periodic table
D. elements maintains its positions

Answer

**Step-by-Step Solution:**

1. **Understanding Alpha Particle Emission**:
- An alpha particle consists of 2 protons and 2 neutrons, which is equivalent to a helium nucleus (4He2).
- When an atom emits an alpha particle, it loses 2 protons and 2 neutrons.

2. **Defining the Initial Atom**:
- Let’s denote the initial atom as X, with atomic number Z and mass number M.
- The atomic number (Z) represents the number of protons, and the mass number (M) represents the total number of protons and neutrons.

3. **Calculating the New Atomic and Mass Numbers**:
- After emitting an alpha particle, the new atomic number becomes \( Z - 2 \) (because it loses 2 protons).
- The new mass number becomes \( M - 4 \) (because it loses 2 protons and 2 neutrons).

4. **Identifying the Element's Position in the Periodic Table**:
- The atomic number determines the position of an element in the periodic table. A decrease in atomic number by 2 means the element moves two places to the left in the periodic table.

5. **Evaluating the Options**:
- Option 1: An element moves two places to the right in the periodic table. (Incorrect)
- Option 2: An element moves one place to the left. (Incorrect)
- Option 3: An element moves two places to the left. (Correct)
- Option 4: Elements maintain their position. (Incorrect)

6. **Conclusion**:
- The correct answer is that when an alpha particle is emitted, the element moves two places to the left in the periodic table.

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