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polarizibility and polarizing

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Rayan:
hello.

Arrange the following in the decreasing order of polarizibility:

Li+  Be 2+     Br-  Cl-    Se 2-

Arrange the following in the decreasing order of polarizing:

Al 3+     Cs+    Cr 3+       Rb+      Sr 2+      Xe

Borek:
Google.

http://notes.chem.usyd.edu.au/course/masters/Chem1/Special%20Topics/Polarizability/Polarizability%20Applications.htm

Rayan:
i'm still confused about it.
in arranging the elements in decreasing polarizing:

Cr > Sr  > Rb > Cs

but who is more polarizing; Al or Xe ?

and in arranging the elements in decreasing order of polarizability:

Se > Br > Cl . what about Li and Be?

am i even close to correct?

jdurg:
Okay.  Basically, an ion is more polarizeable if it has a large electron cloud hanging around the nucleus.  For a big atom with a negative charge, it will be polarized very easily because it will have a lot of electrons around a big central nucleus.  Those outer electrons will feel a bunch of pull from any other nucleus out there.

Positive ions decrease in polarizability as their nucleus size gets smaller.  This is because the outer electrons feel a VERY strong pull from their own nucleus and are less likely to feel the pull of another element's nucleus.

So when you are arranging the atoms/ions in terms of their polarizability, the first thing you must do is determine how many electrons the atom/ion has and what its atomic number.  If you have two atoms/ions with the same number of electrons, but one has a bigger nucleus, based upon the information above which one do you think would be more polarizable?

Rayan:
the one with smaller nucleus will be more polarizable because then they will be more likely to feel the pull of another element's nucleus.
now letme get this straight:
an atom/ion is more polarizable if it is large and has a high charge. correct?
and the atomic radius decrease as we go from left to right in the periodic table, and increases down a group. thus Li is bigger than Be but Be has a higher charge. what is more important? being larger or having a higher charge??
and an atom is more polarizing if it is small. Xe being in group 18 has small radius, but it is in the fifth row while Al is in the third. who is more polarizing?

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