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Coordination Compounds

Posted: Mon Nov 16, 2015 11:02 pm
by Vanessa Romero-Campos 2B
When naming coordination compounds how is it that we get the roman numeral after the cation name? How do we identify it?
For example if we are given [Co(NH3)5Cl]Cl. 2H20 the name for this compound is Penta Ammine Chloro Cobalt(II) Chloride dihydrate. How is it that we get (II) after cobalt?

Re: Coordination Compounds

Posted: Mon Nov 16, 2015 11:17 pm
by Sandeep Gurram 2E
The roman numerals after the cation name specifies the charge that the cation (central atom has). In the problem that you provided, since NH3 has a neutral charge, we are left with two chlorines (one inside the coordination complex, and one outside). These two chlorines amount to a net -2 charge. As the overall compound is neutral, we arrive to the conclusion that the Cobalt must have a +2 charge. This is indicated with the roman numerals (II) after its name, as you have written down.