Place the ions in order of decreasing size. Te2-, I-, Cs+, Ba2+, La3+?

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I am not sure if the answer below is correct: Te^2- > I^- > Cs^+ > Ba^2+ > La^3+ (from biggest to smallest)Below is the answer that I entered and confirmed its incorrect:Cs+ > Ba2+ > La3+ > Te2- > I-

Everardo Feil · Accepted Answer

I believe the answer would be:Te2- > I- > Cs+ > Ba2+ > La3+ (from biggest to smallest)This is what you wrote above. This makes sense because all 5 ions are isoelectronic with xenon (i.e. they all have 54 electrons) but the number of protons (positively charged particles in the nucleus of the atom) of each is different:La3+ has 54 electrons and 57 protons, meaning that there are 3 additional positive charges to attract the negatively-charged electrons, bringing them closer in towards the nucleus (a "stronger" grip, and therefore, smaller-sized ion if you can imagine). Ba2+ has 54 electrons but 56 electrons (only 2 additional positive charges). Cs+ has 54 electrons and only 55 protons (only 1 additional positive charge).I- has 54 electrons and only 53 protons (1 fewer positive charge).Te2- has 54 electrons and only 52 protons (2 fewer positive charges).Anions (negatively charged ions) that are isoelectronic with a particular noble gas (in this case, xenon) are generally larger in size than cations (positively charged ions) that are also isoelectronic with the same noble gas.

Mr. Durward Cummerata

Place the ions in order of decreasing size. Te2-, I-, Cs+, Ba2+, La3+?

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