Nickel 

Nickel is the 22^nd most abundant element in the Earth's crust and the 7th most abundant transition metal. It is a silver-white crystalline metal found in meteorites and combined with other elements in ores. Two main types of ores to extract nickel are laterites, such as sulfide ores, which typically contain 1.5% nickel and are often combined with other metals like copper and cobalt.

1.0Introduction

One of the iron group's glossy, ductile, and malleable metals with a silvery-white appearance is nickel, prized for its high polish. It is an electricity and heat conductor of mediocre quality. Nickel often exhibits a +2 oxidation state in its typical compounds and can also show various valences. Many of the complex compounds that nickel produces are blue or green. Like iron, it dissolves slowly in dilute acids but turns passive in nitric acid. Hydrogen can also be adsorbed by finely split nickel.

Isotopes 

Nickel has five naturally occurring isotopes: nickel-58, nickel-60, nickel-61, nickel-62, and nickel-64. Among these, four are stable: nickel-58, nickel-60, nickel-61, and nickel-62,

Nickel-58 is the most abundant, making up 68% of all-natural nickel. Nickel-60 follows, comprising roughly 26%. Nickel-61 and nickel-62 are rarer, contributing about 1% and 4% to the natural nickel found on Earth.

2.0Physical Properties of Nickel 

3.0Chemical Properties of Nickel

Nickel is a relatively unreactive metal at room temperature. It does not react with oxygen, water, or most acids, but its reactivity increases at higher temperatures. The metal can be polished and does not tarnish in air, making it corrosion-resistant.

Reaction with Water: Nickel metal does not react with water under standard conditions.

Reaction with Air: At room temperature, nickel remains unreactive with air. However, finely divided nickel reacts with air and can become pyrophoric. At elevated temperatures, nickel reacts with oxygen, forming nickel(II) oxide:

2Ni(s) + O₂(g) → 2NiO(s)

Reaction with Halogens: Albeit slowly, nickel reacts with fluorine gas (F₂), making it ideal for fluorine storage tanks. It also reacts with chlorine (Cl₂), bromine (Br₂), and iodine (I₂) to form nickel(II) halides:

• Ni(s) + Cl₂(g) → NiCl₂(s) [yellow]
• Ni(s) + Br₂(g) → NiBr₂(s) [yellow]
• Ni(s) + I₂(g) → NiI₂(s) [black]

Reaction with Acids: Nickel dissolves slowly in dilute sulfuric acid, producing nickel(II) ions, sulfate ions, and hydrogen gas:

Ni(s) + H₂SO₂(aq) → Ni²⁺(aq) + SO₄²⁻(aq) + H₂(g)

4.0Nickel Compounds

Nickel primarily forms divalent compounds, with +2 being its most significant oxidation state. However, nickel can also exhibit oxidation states ranging from -1 to +4. The characteristic colours of nickel compounds are blue and green, often found in hydrated forms.

Water Solubility of Nickel Compounds

• Water-Soluble Compounds: Nickel acetate, nickel bromide, nickel chloride, nickel iodide, nickel nitrate, and nickel sulfate are soluble in water.
• • Hydrated Nickel (II): This is the primary ion in aqueous solutions of nickel compounds.
• Water-Insoluble Compounds: Nickel oxides, hydroxides, sulfides, arsenides, chromate, carbonate, phosphate, and selenide are water-insoluble.

Properties of Specific Nickel Compounds

Nickel Oxide (NiO):

• Solubility: Soluble in acids, potassium cyanide, and ammonium hydroxide; insoluble in cold/hot water and caustic solutions.
• Forms:

Black Nickel Oxide: Chemically reactive.

Green Nickel Oxide: Inert and refractory.

Nickel Acetate (Ni(C₂H₃O₂)₂):

• Solubility: Soluble in acetic acid and water; insoluble in alcohol.
• Decomposition: Decomposes before melting, forming nickel oxide and releasing irritating fumes.

Nickel Carbonate (NiCO₃):

• Solubility: Soluble in dilute acids and ammonia; insoluble in hot water.
• Reactivity: Reacts violently with iodine, hydrogen sulfide, or a mixture of barium oxide and air.

Nickel Hydroxide (Ni(OH)₂):

• Solubility: Soluble in acids and ammonium hydroxide; practically insoluble in water.
• Decomposition: Decomposes to nickel oxide and water when heated at elevated temperatures.

5.0Uses of Nickel

Some of the key uses of nickel:

• Stainless Steel Production Nickel is used to manufacture stainless steel, improving the material's strength and corrosion resistance.
• Batteries: Nickel is a necessary component of several battery types, such as rechargeable nickel-cadmium (Ni-Cd) and nickel-metal hydride (NiMH) batteries.
• Wires and Electronics: Nickel’s malleability and flexibility make it an ideal material for manufacturing wires, commonly used in electrical and electronic applications.
• Superalloys: When combined with iron or cobalt, nickel forms superalloys used in gas turbines and jet engine parts due to their high resistance to heat and durability.
• Everyday Appliances: Nickel is incorporated into everyday items like power tools, camcorders, scanner radios, guitar strings, laptops, and cordless telephones.
• Desalination Plants: Due to their resistance to corrosion in marine environments, copper-nickel alloys are used in desalination plants to convert seawater into freshwater.
• Colouring Agent: Paints, cosmetics, and some plastics contain nickel compounds, such as nickel dimethylglyoxime, as colouring agents.
• Electroplating: To give metals a decorative and protective coating, nickel is a common electroplating material.