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How is the oxidation state of nickel determined in the hexaaquanickel(2+) ion?

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Two diagrams show the three-dimensional structure of a methane molecule: panel A uses a ball-and-stick model with a central carbon atom connected to four hydrogen atoms in a tetrahedral arrangement, while panel B illustrates the bond angle of 109.5 degrees and bond length of 1.09 angstroms between carbon and hydrogen atoms. — chemical compound Methane, in which four hydrogen atoms are bound to a single carbon atom, is an example of a basic chemical compound. The structures of chemical compounds are influenced by complex factors, such as bond angles and bond length.

In the hexaaquanickel(2+) ion, denoted as $[N i (H_{2} O)_{6}]^{2 +}$ , the oxidation state of the central nickel atom is determined by considering the charges of the ligands and the overall charge of the complex ion.1

The calculation follows these principles:
* Ligand Charge: The water molecules ( $H_{2} O$ ) coordinated to the nickel are electrically neutral.1
* Overall Charge: The complex ion $[N i (H_{2} O)_{6}]^{2 +}$ carries a net charge of +2.1
* Calculation: Since the sum of the oxidation states of all atoms in a complex must equal the net charge of the ion, the oxidation state of nickel is calculated as:
$Oxidation state of Ni + 6 \times (charge of H_{2} O) = + 2$
$Oxidation state of Ni + 6 \times (0) = + 2$
$Oxidation state of Ni = + 2$

Thus, the nickel in this coordination compound is in the +2 oxidation state.1