Gold is considered one of the least reactive elements and is classified as an inert metal. It is a rare, attractive, and precious element used for making jewelry and other expensive objects. In earlier times gold was also used for making coins. If you have ever seen thin gold foil and wondered how it is done, don’t worry! I will tell you! So, Is gold malleable? Yes, gold is a malleable metal. In fact, gold is the most malleable out of all the metal elements. Malleability is the property of the metals that refers to their ability to get beaten into thin sheets under the influence of simple force such as hammering. This is due to the arrangement of atoms in the metals, i.e. their lattice structure, which permits redesigning of the entire structure to attain different shapes, also known as plastic deformation. Malleable means “capable of being shaped by hammering, beating, etc.”
Why is Gold Malleable?
The property of the metals to undergo plastic deformation under relatively low stress such as hammering is known as malleability. The metals have the ability to get easily deformed under compression and tension, instead of breaking down like many other elements. Thus, the metals can be rolled into sheets by applying some pressure. When we call gold the most malleable metal we mean that it is able to form the thinnest sheets out of all the metals.
One gram of gold can be rolled to form a sheet as wide as one square meter. The sheets can be so thin that they may become semi-translucent. The reason for the malleability of gold or in fact, any metal is the arrangement of the atoms inside them, also known as the lattice structure. The atoms of gold are arranged in a face-centered cubic lattice. This means that the atoms are held together in layers that are deposited one over the other. As there is no direct linkage between these layers, they easily slide over each other as the pressure is applied. As the pressure increases more and more layers get arranged linearly, and hence, thin sheets are formed. Therefore, the atomic arrangement of gold is responsible for its behavior to get molded into articles of different shapes and sizes. The highest malleability of gold is also one of the reasons for its high price.
Factors Affecting Malleability of Gold
A number of factors are responsible for the malleability of metal or in our case, gold. However, the two foremost important factors that are actually responsible for the malleability of gold are:
• Metallic Bonding
In the earlier section, we were talking about how the atoms inside metals settle as layers one over another. Also, these layers are able to roll over each other which enables metals to undergo plastic deformation. However, you can wonder how can these layers remain together under normal conditions? Actually, these layers are linked to each other through metallic bonding. Metallic bonding, as the name indicates, is specific to metals in which one or more of the valence electrons leave their orbit and start to wander around. These electrons no longer belong to one definite atom but, travel through the authority of all the nearby atoms. As the electrons are not stable at one place, the metallic bonding is a quite weak force to keep the atoms together and that is why, the layers of atoms even after being linked together, are able to slip past each other. It is due to the metallic bonding that all the metals can be reshaped, and exhibit the property of malleability as well as ductility. Let us understand it through the figures given below:
The above figure depicts the arrangement of atoms, in layers, inside gold, under normal course. However, as an external force or pressure is applied the different layers roll or slide over each other, as shown in the figure below:
Now you know how does metallic bonding affects malleability and why is it so important.
• Temperature
When heat is applied to a metal, the atoms inside it gain kinetic energy owing to which they tend to move away from each other. Under these circumstances if an external force is applied that is also intended to spread these atoms away from each other, the entire process becomes easier. This is the reason why metals become more malleable and ductile as the temperature increases. That is why you would have always seen that whenever a metal object is reshaped or molded, it is always heated beyond a certain temperature. The temperature also affects the metals in an adverse manner. This means that you can expect metals to become brittle when the temperature is below a certain temperature. This effect is known as embrittling effect while the temperature is called the transition temperature. The transition temperature is the connection point above which metals are malleable and below which metals are brittle. The graph is shown below clearly depicts the relation between temperature and malleability as well as the ductility of metals.
The change in the malleability of the metals under the influence of temperature can be easily understood by looking at the above graph, also known as the impact transition curve. As seen the malleability increases with the temperature to a certain point after which it becomes constant and similar is the case with brittleness. The transition temperature differs for different metals based on their purity and other related conditions.
The Lattice Structure of Gold
The lattice structure of any element is said to be divided into two parts viz. Bravais lattice and atoms. The Bravais lattice is the space in which the atoms of the element are arranged which is divided into the unit cells. Usually, a unit cell is assumed to be in the shape of a cube inside which the atoms are arranged in different patterns, and each pattern is referred to with different names. The atoms of gold are arranged in the face-centered cubic (FCC) lattice structure. This arrangement can be described with the help of a cube which here symbolizes gold. Now, inside this cube, the gold atoms are located at each of its eight corners, also known as lattice point, and one atom at each of the six faces of the cube (that is why the name, face-centered). The FCC structure of gold appears as given below:
Counting the number of atoms that form the part of each unit cell: The atoms located at the corners contribute 1/8th part of the atom in a unit cell. Also, there are 8 corners. Therefore, 8 X 1/8 = 1 atom Now, the atoms at the face or sides of the cube contribute ½ atoms to the unit cell. As there are 6 faces of the cube, therefore, 6 X ½ = 3 atoms Hence, total number of atoms in one unit cell of gold = 1 + 3 = 4
Malleability Order of Metals
Malleability is the property that allows plastic deformation in the metals without undergoing fractures, i.e. the metals have the ability to mold into a variety of shapes owing to their malleability. As discussed in the previous sections, all the metals are malleable. However, the extent of malleability depends upon a number of factors such as lattice structure, size of the atom, number of valence electrons, etc. If the size of the atoms is large, more electrons will be available for metallic bonding owing to their distance from the nucleus. Similarly, the valence electrons also affect the metallic bonding inside metals. Taking into consideration, the various factors responsible for the malleability of metals they can be arranged in the order of their decreasing malleability as follows:
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Properties of Gold
A few important properties of gold are listed below: • Gold is a bright yellowish colored metal having atomic mass 79. • The melting and boiling points of gold are 1064 °C and 2700 °C, respectively. • It is a very good conductor of heat as well as electricity due to which it is used in making small significant parts of various electrical appliances. • Gold also reflects the heat and light precisely due to which it is used in coating the helmets of astronauts. • Gold is especially in demand owing to its attractive bright shiny appearance which makes it suitable for making jewelry and precious ornamental items. Check out an interesting video on the malleability of Gold.
Conclusion
Malleability is the property of the metals to get beaten into thin sheets under the influence of external force or pressure such as hammering. The arrangement of atoms inside the metals is particularly responsible for their malleability. The possible plastic deformation of metals allows them to attain a variety of shapes. Gold is the most malleable metal in which atoms are arranged in a face-centered cubic lattice arrangement. The atoms inside gold are arranged in the form of layers that are able to slide past each other when external pressure is applied. The two important factors that affect the malleability of gold or other metals are metallic bonding and temperature. Happy Learning!!
