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

Options

A. number of unpaired electrons
B. atomic mass
C. atomic number
D. number of shells

Explanation

To solve the question regarding the change of Zn to Zn²⁺ and what decreases as a result, we can follow these steps:

### Step 1: Understand the Electron Configuration of Zinc (Zn)
Zinc (Zn) has an atomic number of 30. Its electron configuration is:
- **Zn:** [Ar] 3d¹⁰ 4s²

### Step 2: Determine the Electron Configuration of Zinc Ion (Zn²⁺)
When Zinc loses two electrons to form Zn²⁺, it loses the two electrons from the 4s orbital:
- **Zn²⁺:** [Ar] 3d¹⁰

### Step 3: Analyze the Changes in Electron Configuration
Now, let's analyze the changes:
- **Unpaired Electrons:**
- In Zn, the 3d subshell is fully filled (10 electrons), which means there are no unpaired electrons.
- In Zn²⁺, the 3d subshell remains fully filled (10 electrons), so there are still no unpaired electrons.

- **Atomic Mass:**
- The atomic mass of Zn and Zn²⁺ remains the same since mass is not affected by the loss of electrons.

- **Atomic Number:**
- The atomic number of Zn is 30, and it remains 30 for Zn²⁺ since atomic number is defined by the number of protons, which does not change.

- **Number of Shells:**
- Initially, Zn has electrons in the 4th shell (4s²). After losing the 4s electrons, the valence shell effectively changes, as the outermost shell now only contains the 3d electrons.

### Step 4: Conclusion
From the analysis, we can conclude that the change of Zn to Zn²⁺ is accompanied by a decrease in the number of shells that contain valence electrons.

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

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