Final answer:
The effective nuclear charge on the outermost electron of phosphorus (P) is estimated to be close to the number of valence electrons, minus the shielding effect of the inner electrons. The closest option given is 4.8, which accounts for some electron shielding.
Step-by-step explanation:
The question asks about the effective nuclear charge on the outermost electron of phosphorus (P). The concept of effective nuclear charge (Z_eff) is related to the attraction an electron feels from the nucleus, accounting for both the positive charge of the protons and the shielding effect of the other electrons. To estimate this, we can use Slater's rules, which involve a series of steps for calculating the shielding constant and then subtracting this from the atomic number to obtain Z_eff. While specific calculations using these rules are not provided in the reference material, the effective nuclear charge is typically close to the number of valence electrons for elements in the p-block, considering the shielding effect of the inner electrons.
Based on trends in the periodic table and not on explicit calculation, the answer is likely close to the number of valence electrons of phosphorus, which is 5. However, due to electron shielding, the Z_eff would be slightly less. Thus, the closest answer provided is 4.8, option b. Please note that this is an estimated value and a more precise value would require detailed calculations