CBSE Class 11-science Answered
Effective nuclear charge is the net positive force experienced by electron inside an atom.
Atomic number of Scandium = Z = 21
E.C. of Scandium = (1s2)(2s22p2)(3s23p2)(3d1)(4s2)
Effective nuclear charge = Zeff for 4s electron in scandium = Z – S
Where S is shielding effect.
According to Slater’s rule,
S is 0.35 per electron for n orbital
S is 0.85 per electron for n-1 orbital
S is 1 per electron for n-2 and so on orbital
n = 4s = 1 electron
n-1 = 3s23p63d1 = 9 electrons
n-2 = 2s2p6 = 8 electrons
n-3= 1s2 = 2 electrons
S= (1×10) + (0.85×9) + ( 0.35 × 1)= 0.35 + 7.65 + 10 = 18
Hence, Zeff for 4s electron of Scandium = Z−S = 21 – 18 = 3
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