[alan2015]

hey guys, i was just a little confused about this question i have to answer for hwork. so they ask me to point out the smallest and the largest atom/ion from amongst Al atom, F atom, As atom, Cs cation, I anion, and N atom, and to explain the reasoning. So far I have the iodine anion as the largest because the additional electron decreases Zeff. and therefore outer electrons feel less atraction yada yada. I also thought that the cesium cation is only second largest because it loses its only 6s electron and so loses an entire shell, on top of which Zeff. increases and draws the outter electrons further in.

in the end i got iodine anion as largest and fluorine atom as smallest (for obvious reasons). please let me know if this logic makes sense or there is something else im not accounting for.

any feedback is greatly appreciated.

[JustinCh3m]

with certain exceptions (see your text), the ATOMS can be arranged according to the trend.  ATOMS increase in size/radius going from top right of P.Table (smallest) to the bottom left of P.Table (largest).

Now, with the iodine ion (I-), you have to realize that you've added the 6th p electron such that it has same e- configuration as a Xe atom.

So, ignoring the fact that the nucleus still has only 53 protons, what's your best guess where I- ends up in the list of ATOMS you have?