Question

9. The effective nuclear charge felt by a 1s electron of C is
a. 5.30
b. 5.65
c. 5.35
d.5.70
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Answer 1

Answer:

Effective nuclear charge Zeff=Z−S

where Z = atomic number

and S = screening constant

       = 0.35 per electron for electron in nth orbit.

       = 0.85 per electron for electrons in (n - 1)th orbit

       = 1.00 per electron for electrons in (n - 2)th, (n - 3)th, (n - 4)th orbit

       = 0.30 per electron in 1s-orbital (when alone)

This electron is screened by 18 electrons in (n - 1), 8-electrons in (n - 2) and 2-electrons in (n-3)

Thus, σ=8×0.85(n−1)s2p6+1×10(n−1)d10+8×1(n−2)s2p6+2×1(n−3)s2

=26.8

Thus, Z∗=29−26.8=2.2