The effective nuclear charge (Zeff) experienced by a 2s electron in Chlorine (Cl) is 15. This is due to the shielding effect of the inner electrons.
Explanation of Effective Nuclear Charge (Zeff)
The effective nuclear charge (Zeff) represents the net positive charge experienced by an electron in a multi-electron atom. It is less than the actual nuclear charge (Z) due to the shielding or screening effect of other electrons in the atom. Core electrons (those closer to the nucleus) are more effective at shielding outer electrons than electrons in the same shell.
Calculating Zeff for a 2s Electron in Chlorine
Chlorine (Cl) has an atomic number (Z) of 17, meaning it has 17 protons in its nucleus. Its electron configuration is 1s22s22p63s23p5.
To calculate the Zeff experienced by a 2s electron:
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Identify Shielding Electrons: For a 2s electron in Cl, the primary shielding comes from the two 1s electrons. Electrons in the same shell (2s and 2p) also provide some shielding, but the 1s electrons are the most effective.
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Approximate Shielding Effect: For simplicity, we only consider the shielding effect of the 1s electrons. A more precise calculation would use Slater's rules, which assign specific shielding constants for different electron configurations. However, for this simplified explanation, we assume that each 1s electron effectively reduces the nuclear charge by 1.
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Calculate Zeff: Zeff = Z - Shielding, where Z is the atomic number and Shielding is the number of shielding electrons. In this case:
Zeff = 17 (protons) - 2 (1s electrons) = 15
Therefore, the effective nuclear charge experienced by a 2s electron in Chlorine is approximately 15. This means that the 2s electrons "feel" a positive charge of +15 from the nucleus, even though there are 17 protons present. The other electrons partially cancel out the full nuclear charge.
