Atomic Radius

[Temperature101]

Which of the following is ordered correctly in terms of atomic radius, from smallest to largest?

A. Al3+, Al, S, S2-

B. Al3+, S, Al, S2-

C. S, Al3+, S2-, Al

D. S, S2-, Al3+, Al


Why the answer is B but not A?

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[DNA]

Woops, edit. This can be tricky if you're not careful.

Periodic trend of atomic radius decreases from left to right across a row/period. S is further to the right than Al, so it's smaller than Al.

S < Al

S2- results in a considerable increase in the electron shell because of the gain of two electrons. It's very similar in shape to Argon, which as you know is a nobel gas, and is considerably larger than both S and Al.

S < Al < S2-

And as you noticed already, Al3+, having lost three electrons would have the smallest atomic radius.

Al3+ < S < Al < S2-

Choice B.

 

[milski]

It's Zumdahl night tonight...

"Atomic radii decrease in going from left to right across a period. This decrease can be explained in terms of the increasing effective nuclear charge (decreasing shielding) in going from left to right. This means that the valence electrons are drawn closer to the nucleus, decreasing the size of the atom." Z&Z, 8Ed, p-322

 

[Temperature101]

Woops, edit. This can be tricky if you're not careful.

Periodic trend of atomic radius decreases from left to right across a row/period. S is further to the right than Al, so it's smaller than Al.

S < Al

S2- results in a considerable increase in the electron shell because of the gain of two electrons. It's very similar in shape to Argon, which as you know is a nobel gas, and is considerably larger. It's radius is larger than both S and Al.

S < Al < S2-

And as you noticed already, Al3+, having lost three electrons would have the smallest atomic radius.

Al3+ < S < Al < S2-

Choice B.

I got it now...You are correct. I was not careful.

 

[Temperature101]

It's Zumdahl night tonight...

"Atomic radii decrease in going from left to right across a period. This decrease can be explained in terms of the increasing effective nuclear charge (decreasing shielding) in going from left to right. This means that the valence electrons are drawn closer to the nucleus, decreasing the size of the atom." Z&Z, 8Ed, p-322

Thanks...