After `1 alpha` and `2 beta` emissions.

Options

A. mass number reduces by `2`
B. mass number reduces by `6`
C. atomic number reduces by `2`
D. atomic number remains unchanged

Answer

To solve the problem of what happens to an element after one alpha emission and two beta emissions, we can follow these steps:

### Step 1: Define the Initial Element
Let’s assume the initial element has:
- Mass number (A)
- Atomic number (Z)

### Step 2: Analyze Alpha Emission
An alpha particle consists of 2 protons and 2 neutrons. When an element emits an alpha particle:
- The mass number decreases by 4 (A - 4)
- The atomic number decreases by 2 (Z - 2)

So after one alpha emission, the new element will have:
- New mass number = A - 4
- New atomic number = Z - 2

### Step 3: Analyze Beta Emission
A beta particle is an electron emitted from the nucleus, which occurs when a neutron is converted into a proton. When an element emits a beta particle:
- The mass number remains unchanged (A)
- The atomic number increases by 1 (Z + 1)

Since we have two beta emissions, we need to apply this change twice:
- After the first beta emission:
- Mass number = A - 4 (remains the same)
- Atomic number = Z - 2 + 1 = Z - 1
- After the second beta emission:
- Mass number = A - 4 (remains the same)
- Atomic number = Z - 1 + 1 = Z

### Step 4: Combine the Results
After one alpha emission and two beta emissions, the resulting element will have:
- Mass number = A - 4
- Atomic number = Z

### Final Result
Thus, the final state of the element after one alpha and two beta emissions is:
- Mass number = A - 4
- Atomic number = Z

### Conclusion
From the above analysis, we can conclude that the final element has a mass number decreased by 4 and the atomic number remains unchanged.