Write the formula for nickel(II) hydroxide, used in rechargeable battery electrodes.
Ni2+ and OH-: Ni(OH)2. During charging it oxidizes to NiOOH (nickel +3); during discharge it returns to Ni(OH)2 — the +2/+3 shuttle stores the energy.
What Is the Charge of Nickel?
Nickel commonly forms Ni2+ Ni3+ in introductory ionic compounds.
For classroom purposes nickel is Ni2+, giving green solutions and salts like NiCl2 and NiSO4. A +3 state exists in special materials — the cathode of a nickel-metal-hydride battery cycles between +2 and +3 — but +2 owns everyday chemistry.
| Element | Nickel |
|---|---|
| Symbol | Ni |
| Atomic number | 28 |
| Common ionic charge | +2, +3 |
| Common ions | Ni2+, Ni3+ |
Visual reference
Nickel element image and atomic model
Images are used as visual references; charge rules still depend on the compound.
Where Nickel's charge options come from
Nickel is [Ar]3d8 4s2, and shedding the 4s pair to give d8 Ni2+ is far easier than digging into the d shell. The d8 arrangement is comfortable enough that nickel, unlike its neighbors iron and cobalt, rarely bothers with +3 outside engineered materials.
This is a classroom reference range, not an exhaustive list of all oxidation states.
The trap in Nickel problems
Adding a Roman numeral reflexively: 'nickel(II) chloride' is technically fine, but on naming tests 'nickel chloride' is usually accepted precisely because +2 is nickel's only common state. Know your instructor's convention — and never invent NiCl3.
Worked example: Ni in a formula problem
Ni2+ and Ni3+ in real compounds
NiCl2
Nickel chloride
Ni2+ balances chloride ions.
NiO
Nickel oxide
Nickel can form oxides where total positive and negative charge balances.
Questions students ask about nickel
Are US nickels made of Ni2+?
No — coins are a neutral copper-nickel alloy (only 25% nickel!). Ionic Ni2+ appears when the surface corrodes or dissolves, which is also what triggers nickel-allergy skin reactions to jewelry.
Why are nickel solutions green?
Ni2+ in water exists as [Ni(H2O)6]2+, whose d8 electrons absorb red and blue light, letting green pass. Swap water for ammonia and the solution turns violet-blue — same +2 charge, different ligands.
What is nickel's charge when it catalyzes margarine production?
Zero. Hydrogenation catalysts use finely divided nickel metal; H2 and vegetable-oil molecules react on its neutral surface. No ions involved — a reminder that metals do chemistry at charge 0 too.
How do I use this charge in formulas?
Combine positive and negative ions so the total charge is zero — or let the ionic compound calculator do the crossing for you. The full chart lives on the periodic table with charges.
Where this data comes from
Charges and element facts on this page are checked against the primary references below. Found an error? Email hello@periodictablewithcharges.com — corrections ship in the next content update. See how this site is edited.