the number of d electrons in Co is equal to that of

Options

A. s and p electrons in F atom
B. p electrons in Ar
C. d electrons in `Co^(2+)`
D. total number of electrons in 0 atom

Answer

To solve the question, we need to determine the number of d electrons in cobalt (Co) and compare it with the number of electrons in the other options provided.

### Step 1: Determine the Atomic Number and Electronic Configuration of Cobalt
Cobalt (Co) has an atomic number of 27. Its electronic configuration can be written as:
\[ \text{Co: } 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 3d^7 \, 4s^2 \]

### Step 2: Identify the Number of d Electrons in Cobalt
From the electronic configuration, we can see that cobalt has 7 electrons in the 3d subshell. Therefore, the number of d electrons in cobalt is:
\[ \text{Number of d electrons in Co} = 7 \]

### Step 3: Analyze the Options
Now, we need to compare the number of d electrons in cobalt with the options provided:

1. **S and P Electrons in Fluorine (F)**:
- Fluorine has an atomic number of 9, with the electronic configuration:
\[ \text{F: } 1s^2 \, 2s^2 \, 2p^5 \]
- Total s and p electrons = 2 (from 1s) + 2 (from 2s) + 5 (from 2p) = 9.
- This does not match with 7.

2. **P Electrons in Argon (Ar)**:
- Argon has an atomic number of 18, with the electronic configuration:
\[ \text{Ar: } 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \]
- Total p electrons = 6 (from 2p) + 6 (from 3p) = 12.
- This does not match with 7.

3. **D Electrons in Cobalt (Co²⁺)**:
- Cobalt (Co²⁺) has lost 2 electrons, typically from the 4s orbital. Thus, its atomic number becomes 25.
- The electronic configuration for Co²⁺ is:
\[ \text{Co²⁺: } 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 3d^7 \]
- The number of d electrons in Co²⁺ is still 7.
- This matches with the number of d electrons in Co.

4. **Total Number of Electrons in Oxygen (O)**:
- Oxygen has an atomic number of 8, with the electronic configuration:
\[ \text{O: } 1s^2 \, 2s^2 \, 2p^4 \]
- Total electrons = 8.
- This does not match with 7.

### Step 4: Conclusion
The only option that matches the number of d electrons in cobalt is the d electrons in Co²⁺, which is also 7. Therefore, the correct answer is:
\[ \text{The number of d electrons in Co is equal to that of d electrons in Co²⁺.} \]

### Final Answer
**Option C: d electrons in Co²⁺**