The Correct Answer for Calculate zeff for the 4s electron in a copper atom, cu.
I presume that you are employing Slater’s rules for effective nuclear charge. The general idea is to subtract the effect of shielding from the genuine nuclear charge, Z . The formula for s and d electrons is different, but it has the same number of protons as copper, Z = 29.
If you need to store the information in electron configurations for future reference, it is recommended that you write them out on paper.
Cu: 1s2 2s2 2p6 3s2 3p6 3d10 4s1
For the 4s electron:
29 – [18(0.85) + 10(1.0)] = 3.7
For the 3d electron:
29 – [9(0.35) + 18(1.0)] = 7.85
The 4s electron has a lower-than-average atomic charge, so it has a higher probability of being destroyed than the 3d electron, should the copper ion become dissociated.
we can write it as
here Z is the Atomic number of the element
S is shielding constant
For Cu atom
Z will be 29
and configuration will be
1s2 2s2 2p6 3s2 3p6 3d10 4s1
So the electrons with the same group shield will be 0.35
the electrons with n-1 group shield will be 0.85
the electrons with n-2 or lesser group shield will be 1
so, Zeff for 4s electron will be
Zeff= 29 – ( 18(0.85) + 10(1.0) )
Zeff = 3.7
Zeff for the 4s electron in a copper atom, cu will be 3.7.