oxidation number

[Aya Watson 2B]

Hi can someone please help me with identifying the oxidation number of [CrCl3(NH3)2(OH2)]+
Thank you!

[Ayaan_Ekram_2J]

Hello!

For this problem we must look at the charge of the overall coordination compound and each ligand. We know that NH3 is neutral, OH2 — which is H2O — is also neutral, and each of the three Cl ions has a charge of -1. As the overall charge of the compound is +1 and we only have -3 charge, the charge of Cr must be +4 to make the overall charge +1. I hope this helps!

[WendyN_L2]

It is helpful to know some oxidation rules. When compounds are neutral, there's no plus or minus, such as NH3 and OH2 the oxidation state is zero, in comparison Cl is an ion, and it has an overall -1 charge. O is usually always -2 unless in H2O2 or Fluorine. With that information the only charge is Cl3 so -3 and you want an overall charge of +1, so Cr is +4. Hope that helps

[Rose Arcallana 2B]

Happy Sunday!

This is actually a simple compound to find the oxidation number.
1. I first find the overall charge of the complex, in this case it is +1
2. Then I do is always try to draw the lewis structure for each component of the complex if I don't know the charge. NH3 has a formal charge of 0, so it is a neutral compound, so the 2 NH3 is each contributing 0 charge. OH2 is also a neutral atom, so a contribution of 0 charges. HOWEVER, Cl is an anion with a -1 charge * 3 because of the # Cl atoms
3. If the overall charge is 0 and the ligands are 0*2 + 0*1 + -1*3 = -3, the metal has to have + charge that will equate to +1 when combined, thus Cr has an oxidation state of +4 :)