Final answer:
The approximate nuclear effective charge (Zeff) for a valence electron in the 5d sublevel of tungsten (W) is calculated as 4+, by subtracting the shielding effect of 70 inner electrons from the atomic number of 74.
Step-by-step explanation:
The approximate nuclear effective charge for one of the valence electrons of tungsten (W) in the 5d sublevel can be calculated using the concept of effective nuclear charge (Zeff).
Tungsten has an atomic number (Z) of 74. To find the Zeff for a valence electron in the 5d sublevel, we need to account for the shielding effect of the inner electrons.
As a first approximation, the inner electrons are assumed to completely shield the valence electron from the nuclear charge, except for the 2 electrons in the same shell that contribute to the 5d sublevel. This results in an effective nuclear charge Zeff = Z - shielding electrons.
Considering the electron configuration of tungsten [Xe]4f145d46s2, there are 54 electrons from the Xe core, 14 from the 4f sublevel, and 2 from the 6s sublevel that shield the 5d valence electrons, summing up to 70 electrons. Thus, the effective nuclear charge for a valence electron in tungsten's 5d sublevel would be approximately 74 (atomic number) - 70 (shielding electrons) = 4+