For the electrons of oxygen atom, which of the following statements correct?

Options

A. `Z_(eff)` for an electron in a 2s orbital is the same as `Z_(eff)` for an electron in a 2p orbital.
B. An electron in the 2s orbital has the same energy as an electron in the 2p orbital.
C. `Z_(eff)` for an electron in 1s orbital is the same as `Z_(eff)` for an electron in a 2s orbital.
D. The two electrons present in the 2s orbital have spin quantum numbers, `m_(s)` but of opposite sign.

Explanation

To determine which statements about the electrons of an oxygen atom are correct, we will analyze each statement based on the electronic configuration of oxygen and the principles of atomic structure.

### Step-by-Step Solution:

1. **Identify the Electronic Configuration of Oxygen:**
- Oxygen has 8 electrons. The electronic configuration is:
\[ 1s^2 \, 2s^2 \, 2p^4 \]

2. **Evaluate Statement A:**
- **Statement A:** "Z effective for an electron in 2s orbital is the same as Z effective of an electron in 2p orbital."
- **Analysis:** The effective nuclear charge (Z effective) is higher for electrons in orbitals closer to the nucleus. Since the 2s orbital is closer to the nucleus than the 2p orbital, the Z effective for 2s will be greater than that for 2p.
- **Conclusion:** This statement is **incorrect**.

3. **Evaluate Statement B:**
- **Statement B:** "An electron in the 2s orbital has the same energy as an electron in the 2p orbital."
- **Analysis:** The energy levels of orbitals can be determined using the formula \( n + l \). For 2s, \( n + l = 2 + 0 = 2 \) and for 2p, \( n + l = 2 + 1 = 3 \). Since these values are different, the energies are not the same.
- **Conclusion:** This statement is **incorrect**.

4. **Evaluate Statement C:**
- **Statement C:** "Z effective for an electron in 1s orbital is the same as in 2s orbital."
- **Analysis:** The 1s orbital is closer to the nucleus than the 2s orbital, hence the Z effective for the 1s orbital will be greater than that for the 2s orbital.
- **Conclusion:** This statement is **incorrect**.

5. **Evaluate Statement D:**
- **Statement D:** "The two electrons present in the 2s orbital have the same spin quantum number but the opposite sign."
- **Analysis:** According to the Pauli Exclusion Principle, no two electrons in the same orbital can have the same set of quantum numbers. Therefore, the two electrons in the 2s orbital must have opposite spins. They will have the same spin quantum number (1/2) but opposite signs (+1/2 and -1/2).
- **Conclusion:** This statement is **correct**.

### Final Answer:
The correct statement regarding the electrons of the oxygen atom is **Statement D**.

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