Total Number of unpaired electrons in `d-` orbitals of an atom element of atomic number 29 is `:`

Options

A. Ten
B. One
C. Zero
D. Five

Explanation

To find the total number of unpaired electrons in the d-orbitals of an atom with atomic number 29, we first need to determine the electron configuration of the element.

### Step-by-step Solution:

1. **Identify the Element**:
The atomic number 29 corresponds to the element Copper (Cu).

2. **Determine the Electron Configuration**:
The electron configuration of Copper can be written as:
\[ \text{Cu: } [\text{Ar}] \, 4s^1 \, 3d^{10} \]
Here, the configuration shows that Copper has one electron in the 4s orbital and ten electrons in the 3d orbital.

3. **Understand the Filling Order**:
Generally, electrons fill the 4s orbital before the 3d orbitals. However, Copper is an exception due to its stability preference, where one electron from the 4s orbital is promoted to the 3d orbital.

4. **Count the Electrons in the d-Orbitals**:
The 3d subshell can hold a maximum of 10 electrons. In the case of Copper, it has 10 electrons in the 3d subshell, which means it is completely filled.

5. **Determine Unpaired Electrons**:
Since the 3d subshell is fully filled (10 electrons), there are no unpaired electrons in the d-orbitals.

### Final Answer:
The total number of unpaired electrons in the d-orbitals of Copper (atomic number 29) is **0**.

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