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Metals – Metallic bonds and the properties of metals

Gold Bar Lot

Metals in the periodic table

In the periodic table, elements can be classified into metals, non metals and metalloid. Almost 80% of the elements in the periodic table are metals. All atoms from column 1 to column 12 are metals except the hydrogen atom which is non metal. After the column 13 or group 3, there is a stair-stepped line starting with the aluminium metal and going all the way down to Polonium (Po). All the elements to the left of that line can be classified as metals. In the photo below you can see the line that divides the periodic table and shows the metals.

Metals - Metallic bonds and the properties of metals

Metals around us

There is so many objects around us formed with metals, like jewelleries, windows, doors, some kitchen utensils, electrical wires, coins, chairs, tables, laptops, cars, and so many other objects used in our daily life.

Metals - Metallic bonds and the properties of metals

Metallic bonds

Metals are elements that form positive ions (cations), and the bonds between the atoms of metals are called “metallic bonds”. Metallic bonds are different than the covalent and the ionic bonds. This type of bond gives metals there specific properties.

To form positive ions, metals lose electrons, the valence electrons of metal atoms are called delocalized electrons because they can move freely from one part of the metal to another, they can move around the cations. So metal cations are surrounded by delocalized electrons and form the “sea of electrons”. Metallic bonds consist of the attraction between the delocalized electrons and the positively charged metal ions (cations). This attraction is the “bond” that holds metals together.

Metals - Metallic bonds and the properties of metals

Properties of metals

Melting and boiling point

In general, metals have moderately high melting points and high boiling points.

Melting point: It is the temperature at which a solid becomes a liquid at normal atmospheric pressure.

Boiling point: It is the temperature at which a liquid boils and changes to a gas.

ElementMelting Point (0C)Boiling point (0C)
Lithium1811,342
Sodium 98883
Aluminium 6552,425
Barium 7271,805 
Silver 960.8 2,212
Copper 1,0832,595
Melting and boiling points for some metals

Malleability and ductility

Metals are malleable, they can be hammered into sheets. They are also ductile, so they can be drawn into wire. An applied force causes metal ions to move through delocalized electrons, making metals malleable and ductile because of the metallic bond.

Metals - Metallic bonds and the properties of metals

Electrical conductivity

Because delocalized electrons are free to move, they can travel through the lattice of the metal. Under an electric field, these electrons move through the metal, passing an electric charge as they move. So metals are good conductors of electricity. The table below presents the conductivity and the resistivity* of certain metals.

*Resistivity: This is the opposite of conductivity, it shows how strongly a metal resists to the flow of electric current. Resistivity is represented by the Greek letter rho (ρ).

Metal Resistivity
p(Ω•m) at 20°C
Conductivity
σ(S/m) at 20°C
Silver 1.59×10-86.30×107
Copper 1.68×10-85.98×107
Gold 2.44×10-84.52×107
Aluminium2.82×10-83.5×107
Calcium 3.36×10-82.82×107
Magnesium4.66×10-82.15×107
Zinc 5.945×10-81.682×107
Resistivity and conductivity of some metals. Source : ThoughtCo., 2020, Electrical Conductivity of Metals. [Online]

Thermal conductivity

Metals are good conductors of heat, because the delocalized electrons can move freely throughout the solid and thus transfers the thermal energy at a very high rate as compared to insulators. 

Metals alloys

An alloy is a mixture of elements that has different metallic properties. The properties of alloys generally differ from the properties of the elements that they contain. They are important because their properties are often superior to the properties of their component elements.

For example, sterling silver is harder and more durable than pure silver. Brass is harder and easier to shape than either copper or zinc.