When a `beta`-particle is emitted by an atom of a radioactive element, the daughter nuclide formed possesses:

Options

A. same mass number but atomic number less by one unit
B. same mass number but atomic number less by two units
C. same mass number but atomic number higher by one unit
D. same mass number but atomic number higher by two units

Answer

To solve the question regarding the emission of a beta particle by a radioactive element and the characteristics of the daughter nuclide formed, we can follow these steps:

### Step 1: Understand Beta Emission
When a beta particle (β) is emitted from a radioactive atom, it involves the transformation of a neutron into a proton within the nucleus. This process can be represented as follows:
- A neutron (n) in the nucleus is converted into a proton (p) and a beta particle (β), which is an electron.

### Step 2: Analyze the Atomic Number and Mass Number
Let’s denote the parent nuclide as Y, with atomic number A and mass number M:
- Parent nuclide: \( _{A}^{M}Y \)

After beta emission, the daughter nuclide (Z) will have:
- Atomic number: \( A + 1 \) (since a neutron is converted into a proton)
- Mass number: \( M \) (the mass number remains unchanged because the total number of nucleons (protons + neutrons) does not change)

### Step 3: Formulate the Daughter Nuclide
The daughter nuclide can be represented as:
- Daughter nuclide: \( _{A+1}^{M}Z \)

### Step 4: Conclusion
From the above analysis, we conclude:
- The daughter nuclide formed after beta emission possesses the same mass number (M) as the parent nuclide but an atomic number (A) that is increased by 1.

### Final Answer
The daughter nuclide formed possesses:
- Same mass number but atomic number increased by 1.