Amongst the following, identify the species with an atom in +6 oxidation state:

\(CrO_2Cl_2\)

The correct answer is (4), \(CrO_2Cl_2\).

The oxidation state of an atom is the number of electrons that an atom has lost or gained in order to form a chemical bond. The oxidation state of Cr in \(CrO_2Cl_2\) is +6. This can be calculated by assigning oxidation states to each of the atoms in the molecule.

• Oxygen has an oxidation state of -2.
• Chlorine has an oxidation state of -1.
• Therefore, the oxidation state of Cr must be +6 in order for the molecule to be electrically neutral.

The other options do not have an atom with an oxidation state of +6.

• \(MnO_4^–\) has an oxidation state of +7 for Mn.
• \(Cr(CN)_6^{3–}\) has an oxidation state of +3 for Cr.
• \(NiF_6^{2–}\) has an oxidation state of +4 for Ni.