Answer:
-3
Explanation:
The oxidation state or oxidation number of an atom is the total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom.
The complex anion here is [Cr(CN)6]3-.
Now, as the oxidation state of CN or cyanide ligand is -1, and if we suppose the oxidation state of Cr to be 'x', then; x - 6 = -3 (overall charge on the anion),
so x= +3. Hence the oxidation state of Chromium in this complex hexacyanochromium (III) anion comes out to be -3.
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The element in the periodic table with the provided electron configuration is Chlorine. Cl it is found as in element in Group 7 of the periodic table.
3. I am not sure what is meant by shape, it could be to do with structure.
4. It is magnesium nitride, as adding nitrogen makes a nitride
Depending on the strictness of your teacher you can name it as either of the following:
2-methyl-propane or iso-propane
Bromide gives away 1 electron (valency of 1) and Ca wants to gain 2 electrons (valency of 2) therefore 2 Br ions are needed