Calculate the Zeff (Z*) for 4s electron of chromium atom (Slater's Rule)?

 Step (1): Write the electronic configuration of Chromium (Cr) in the appropriate form.

Cr: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵ 

Cr: (1s²)(2s²,2p⁶)(3s²,3p⁶,3d⁵)(4s¹)

Step (2): Use the Slater Rule to calculate the shielding constant for the electron.

 (S)_4S = (4s electrons-1)x 0.35+ ( electrons of penultimate shell)x 0.85 +(remaining electrons) x 1.00 

(S)_4s = (1-1)x 0.35+ (13)x 0.85+ (10)x 1.00 = 21.05

                                   Thus Z* =Z-S = 24-21.05 = 2.95

What is the shielding constant (S) experienced by a 3d electron in the bromine atom?

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