In which orbital does an electron in a phosphorus atom experience the greatest effective nuclear charge?

a. 1s
b. 2s
c. 2p
d. 3s
e. 3p

I originally thought 3p, since those are the outer electrons, but that was marked wrong. Why is it not 3p? Is the right answer 3s then?

6 answers

1s, right?

The 3p is right for the LEAST effective nuclear charge (remember those outer electrons aren't held strongly) but this is the opposite of that; therefore, the correct answer is 1s. There is no shielding for the 1s electrons. (Technically, the other electron in the 1s does offer some shielding; however, those 1s electrons SEE the highest pull from the protons in the nucleus.

1s. because it is the nearest orbital to nucleus