Predict Zeff for the outermost electrons in the Rb atom based on the calculations for Na and K using Slater's rules.
To predict the effective nuclear charge (Zeff) for the outermost electrons in the Rb (Rubidium) atom, we can use Slater's rules. Slater's rules provide an empirical method to estimate the effective nuclear charge experienced by an electron in a multi-electron atom.
To apply Slater's rules, we need to follow these steps:
1. Write the electron configuration: The electron configuration for Rb is 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^1.
2. Identify the valence electrons: The outermost electrons are those in the highest energy level, which is the 5s orbital. In the case of Rb, there is only 1 valence electron.
3. Apply Slater's rules:
- Rule 1: Electrons in the same group (vertical column) do not effectively shield each other. Therefore, the 4s, 3d, and 4p electrons do not effectively shield the 5s electron.
- Rule 2: Electrons in inner energy levels (closer to the nucleus) effectively shield outer electrons. In Rb, the electrons in the 1s-4p orbitals act as inner or core electrons and thereby shield the 5s electron.
- Rule 3: Electrons in the same energy level do not effectively shield each other. Thus, the 5s electron does not shield the 5s electron.
4. Assign shielding values:
- Core electrons (1s-4p): Assign a shielding value of 0.35 (or 0.30 if non-metal).
- Electrons in the same energy level: Assign a shielding value of 0.85.
5. Calculate Zeff:
- For the 5s electron, there are no other electrons in the same energy level, so the shielding value is 0.85.
- There are 36 core electrons (1s-4p orbitals) that effectively shield the 5s electron. Therefore, the core contribution to Zeff is 36 * 0.35 = 12.6.
Zeff = Z - Core shielding
Zeff = 37 - 12.6
Zeff ≈ 24.4
Therefore, the predicted effective nuclear charge (Zeff) for the outermost 5s electron in the Rb atom is approximately 24.4 based on the calculations using Slater's rules.