Calculate the effective nuclear charge on a valence electron in an oxygen atom.
The Correct Answer and Explanation is:
To calculate the effective nuclear charge (Z_eff) on a valence electron in an oxygen atom, we use the formula:Zeff=Z−SZ_{\text{eff}} = Z – SZeff=Z−S
Where:
- ZZZ is the atomic number (the number of protons in the nucleus),
- SSS is the shielding constant, which accounts for the electrons that shield the valence electron from the full charge of the nucleus.
Step 1: Find ZZZ
For an oxygen atom, the atomic number ZZZ is 8. This means oxygen has 8 protons in its nucleus and 8 electrons in total.
Step 2: Determine the electron configuration
The electron configuration of oxygen is:1s22s22p41s^2 2s^2 2p^41s22s22p4
The valence electrons are in the 2s2s2s and 2p2p2p orbitals, and there are 6 valence electrons in total.
Step 3: Determine the shielding constant SSS
The shielding constant SSS represents the effect of the inner electrons (those in the 1s1s1s orbital) in reducing the full nuclear charge experienced by the valence electron.
- Electrons in the same shell (the 2s2s2s and 2p2p2p electrons) provide a small shielding effect. For simplicity, in this calculation, we assume they contribute a partial shielding value.
- The two electrons in the 1s1s1s orbital provide the most significant shielding.
For oxygen, we can use an approximation of S=2S = 2S=2, as the 1s electrons significantly shield the 2s and 2p electrons, while the 2s and 2p electrons provide minimal shielding for one another.
Step 4: Calculate ZeffZ_{\text{eff}}Zeff
Using the formula:Zeff=Z−S=8−2=6Z_{\text{eff}} = Z – S = 8 – 2 = 6Zeff=Z−S=8−2=6
Conclusion:
The effective nuclear charge on a valence electron in an oxygen atom is 6. This means the valence electron experiences an effective nuclear charge of 6 units, which is less than the full charge of the nucleus (8 units) due to the shielding effect of the inner electrons. This value of ZeffZ_{\text{eff}}Zeff helps explain the chemical behavior of oxygen, including its tendency to form bonds and attract electrons in reactions.
