Nickel

The metal in stainless steel and rechargeable batteries, and a quarter of the coin named after it.

At a glance

Symbol: Ni
Atomic number: 28
Average atomic mass: 58.69
Group: 10
Period: 4
Family: transition metal
Electron configuration: [Ar] 3d⁸ 4s²
Electronegativity: 1.91
Common ions: Ni²⁺, green in solution

On the table

Period 4, group 10. The other transition metals are tinted, and every cell opens its own article.

Electrons and bonding

Nickel has 28 electrons, one for every proton, so the atom carries no charge. Below are the same 28 electrons written two ways.

Simple form: electrons per shell

shell 12shell 28shell 316shell 42

Counting outward from the nucleus: 2, 8, 16, 2. The outer shell is picked out.

Orbital form: electrons per subshell

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸ 4s²

Short form: [Ar] 3d⁸ 4s², where [Ar] stands for the 18 electrons argon already has.

That list runs by shell. In the order the subshells fill it reads [Ar] 4s² 3d⁸, because a subshell fills by its energy, not by its shell number.

3d⁸↑↓↑↓↑↓↑↑

4s²↑↓

The boxes hold the electrons beyond [Ar]. Each box is one orbital and takes two electrons at most, spinning opposite ways. They spread out singly before they pair up.

How to read the two

The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 3 here is 3s² 3p⁶ 3d⁸, and 2 + 6 + 8 is 16.

Nickel sits in period 4 and has 4 shells. The period number counts the shells.

What that means for bonding

The outer shell holds 2 electrons. Those are the ones nickel can lose, gain or share, so they are the ones that decide what it bonds with.

Like other transition metals, nickel loses its outer s electrons, and often some d electrons as well, to form positive ions, and it can form more than one kind.

Properties

State at 25 °C: solid
What it looks like: silvery-white metal with a faint golden tint, hard and slow to corrode
Melting point: 1455 °C
Boiling point: 2913 °C
Density: 8.91 g/cm³
Magnetic: yes, like iron and cobalt

Where it is found

Mined from sulfide ores such as pentlandite and from weathered laterite soils; Indonesia is now the largest producer. Earth's core is thought to be about 5% nickel, and iron meteorites contain it. The rich ore field at Sudbury, Canada, sits in an ancient impact crater.

Discovery and name

Axel Fredrik Cronstedt isolated it in 1751 from a reddish ore that German miners called kupfernickel, Old Nick's copper, because it looked like copper ore but yielded no copper. He shortened the name to nickel.

What it is used for

About two thirds goes into stainless steel. Nickel also makes superalloys for jet engines, rechargeable batteries (nickel-metal hydride and nickel-rich lithium-ion), plating, and the catalysts that harden vegetable oils. The US five-cent coin is 75% copper and only 25% nickel.

In compounds

NiSO₄nickel(II) sulfate, for platingNiOnickel(II) oxideNiCl₂nickel(II) chloride, greenNi(CO)₄nickel carbonyl, very toxicNiO(OH)nickel oxyhydroxide, a battery electrode

Handle with care

Nickel is one of the most common causes of skin allergy from jewelry and watchbands. Nickel carbonyl gas is extremely poisonous.