What is the charge of iron in the following complex: [Fe(H2O)6]Cl2 ?
When attempting to answer a question about complexes, you need to think about three things: the identity of the metal (and its oxidation number), type of ligand (i.e. if it's neutral like H2O or has a negative charge like Cl-, if it's monodentate or polydentate) and the charge of the whole complex.Let's start from the end: charge of the complex isn't stated so you need to figure it out from the counter-ion, which is chloride, Cl-. In order to balance the charge of 2 chloride ions (-1 each), we need a +2 charge, so this is the charge of the complex. The type of ligand in this case is just water, a neutral molecule (i.e. its charge = 0). Therefore, if the whole complex has a charge +2 and the ligand has charge 0, it means that the +2 charge comes from the metal: Fe 2+.
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