How do you find the ionic charge of an element?

Ive got a test tommorow in Chem and im gonna fail. so does anybody know how to find this?



example. NaCl whats the ionic charge and why?



do you use the periodic table? help please!How do you find the ionic charge of an element?
There are some rules/guidelines on your book. It says the common charges on some atoms/ions. Example, oxygen usually have 2-, Hydrogen usually has 1+, etc. etc. etc.

Read it now!



When you know these ones, you can find the charge on the ion (oxidation state?).

Ex.

Cr2O3, a neutral compound so Zero Net Charge.

O has 2- charge, as we know. But there are 3 O in total, so 3 times 2- charge is 6- charge.



Now, there are two chromium. Let x be the charge of Chromium.

2x charge + 6- charge must equal to Zero (since Zero Net Charge).

So, x has to be 3+. The Chromium has 3+ in this case.





For NaCl, you will know that Cl has 1- since it is in the 7th group, which means that it needs 1 more electron to become stable and it is a non-metallic atom. Non-metallic ions are anions (negative ions), so negative charges.

NaCl has Zero Net Charge, since it is neutral. Let x be the charge of Na.

There is 1 Na and 1 Cl.

1(x) + 1(1-) = 0

So, x has to be 1+. Na has 1+ charge.



Usually, we look at the anions first. Then, solve for the charge of the cations (positive ions -- for metals).



Note that some transitional elements have different charges, if that have any importance.How do you find the ionic charge of an element?
The charge on the Na ion is 1, and the charge on the Cl ion is -1. Yes, you use the periodic table. The column to the left of the periodic table generally have electronegativity of -1. And elements in column 1 (to the far left of the table) tend to have electronegativity of 1.



-John
In the first column of the periodic table, all ionic atoms take a +1 charge, in the second column they take a +2 charge. In the last column before the noble gases they take a -1 charge. Many good periodic tables will have these values marked, but many do not. Many of the elements in the middle portions of the table can have different charges depending on something called oxidation state, so for those it is best just to look them up on a table or memorize them. There are rules that govern how those things work, but they are pretty complicated and unless you plan on being an inorganic chemist, you will probably not need to know them.
In a binary compound the first element has a positive oxidation number, and the second element has a negative oxidation number. The sum of the oxidation numbers will always add up to zero for a compound.



In NaCl, Na is +1 and Cl is -1.



PT is a great help to find the oxidation number or the ionic charge. The Roman numerals at the top of the columns tell you the highest oxidation number of the metals. (Except for the three columns of VIIIB.) Subtract the Roman numeral from 8 to get the negative oxidation number for groups IVA through VIIA.



Sorry. Does your PT only have the columns labeled as 1 - 18. I hate it when they do that. Oxidation number equal to the column number up through 7, then subtract 10 from the column number to get the oxidation number of the metals. Subtract the column number from 18 to get the negative oxidation number for the nonmetals.