Which of the following has the largest radius?
a) Cl-
b) K+
c) Ar
d) P3-
e) S2-

They all have the same number of electrons so that's why I'm confused. I know size increases as you go down the periodic table and increases as you go from right to left.

Question

Which of the following has the largest radius?
a) Cl-
b) K+
c) Ar
d) P3-
e) S2-

They all have the same number of electrons so that's why I'm confused. I know size increases as you go down the periodic table and increases as you go from right to left.

anonymous · Answer

the most negative ion which would be P3-. Because it has more electrons around the nucleus its bigger.

anonymous · Answer

You're being asked to understand the role of effective nuclear charge.  Sure, they all have the same number of electrons.  But they don't have the same number of protons in the nucleus, do they?  How does the charge on the nucleus change as you move from P3- to K+?  What effect on the electrons do you think this change in charge has?  How does it change where they orbit?