A change of Zn to `Zn^(2+)` is a accompanied by a decrease in:

Options

A. Number of valence electrons
B. atomic mass
C. Atomic number of element 'X' is 118
D. number of shells

Answer

To solve the question regarding the change of Zn to Zn²⁺ and the accompanying decrease, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Atomic Number of Zinc (Zn)**:
- Zinc has an atomic number of 30, which means it has 30 protons and 30 electrons in its neutral state.

2. **Determine the Electron Configuration of Zinc**:
- The electron configuration of Zn can be written as:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰
- This shows that Zn has a total of 30 electrons distributed across its shells.

3. **Identify the Valence Electrons**:
- The outermost shell (n=4) contains 2 electrons in the 4s subshell. Therefore, Zn has 2 valence electrons.

4. **Conversion to Zn²⁺**:
- When Zn loses 2 electrons to form Zn²⁺, these electrons are removed from the outermost shell (4s).
- The electron configuration of Zn²⁺ will be:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰
- This indicates that Zn²⁺ has lost its 4s electrons.

5. **Analyze the Changes**:
- **Valence Electrons**: The number of valence electrons decreases from 2 to 0.
- **Number of Shells**: The outermost shell (n=4) is now empty, but the total number of electron shells remains the same (there are still 4 shells).
- **Atomic Mass**: The atomic mass remains unchanged because it is determined by protons and neutrons, not electrons.
- **Atomic Number**: The atomic number remains the same as it is defined by the number of protons.

6. **Conclusion**:
- The decrease is observed in the number of valence electrons (from 2 to 0) and the effective outer shell (as the 4s shell is now empty).

### Final Answer:
The change of Zn to Zn²⁺ is accompanied by a decrease in the number of valence electrons.