Ch 2 - what ions to memorize?

[robert zellmer]

I've had a couple of questions about what ions to memorize, both monatomic
and polyatomic.  I did cover this in class.

You are suppose to have memorized the first 30 elements the first week.
For the monatomic ions you should know the elements in group 1A and 2A
and the fact they form +1 and +2 ions in ionic compounds (H is not a metal
but can be +1 and -1 in compounds, actually in ionic compounds it's -1 and
+1 in solution).  There were three metals which always have the same charge
in ionic compounds, Al^3+, Zn^2+ and Ag^+.  Other metals can generally
have more than one charge (oxidation #) in compounds.  I went over this
for representative metals in groups 3A-6A (e.g. Pb can be a +2 or +4,
positive charges equal to the group # and group#-2).

You should know anions for groups 5A, 6A and 7 A (nonmetals in those
groups form anions).  While not in that table, P can be a -3 ion (P^3-) but
it doesn't form anions as readily as N.

The info above is in Fig. 2.19.  Table 2.4 also has examples of the most
commonly used cations, although there are additional ones in that table
I covered in class and just stated above you should know.

Common anions are in table 2.5.  That table is not all inclusive.

I went over which polyatomic ions you should know in class.  There
were five given (same as the ones in Fig. 2.24) in class which you can
use to figure out many others without memorizing them by knowing the
rules when the number of oxygen atoms change.  Also, remember that
atoms in groups tend to form similar compounds and ions.  That means
you should know something like IO3^- is iodate (similar to ClO3^-,
chlorate, as done in lecture).  That applies to many other things which
aren't explicitly shown in the book.  I discussed this in lecture. Not
coming to lecture does not preclude you from knowing what was discussed
in lecture.   Plus, there are homework problems which have several
examples of naming compounds with polyatomic ions not explicitly
discussed in the chapter itself.

You should be thinking about the fact that elements in a group form
similar compounds and undergo similar reactions.  This applies as well
to reactions we covered in chapter 3.

Dr. Zellmer