The study of coordination compounds is an important aspect of Chemistry Topics, as it examines the bonding and reactivity of metal complexes.
Comparison of Physical Properties of Metals and Non-Metals
Metals and non-metals show different physical properties. The important physical properties of metals and non-metals are given below.
(i) Metals are Malleable. This means that metals can be beaten into thin sheets with a hammer.
If we take a piece of aluminium metal, place it on a block of iron and beat it with a hammer, we will find that the piece of aluminium metal turns into a thin aluminium sheet, without breaking. And we say that aluminium metal is malleable or it shows malleability. The property which allows the metals to be hammered into thin sheets is called malleability. Malleability is an important characteristic property of metals.
Most of the metals are malleable. Gold and silver are the best malleable metals and can be hammered into very fine sheets or foils. Aluminium and copper are also highly malleable metals. For example, aluminium metal can be hammered to form thin aluminium foils. Copper metal can also be hammered to form copper sheets. Iron is also a quite malleable metal which can be hammered to form iron sheets. Figure.
Metals can be hammered into It is due to the property of malleability that metals can be bent sheets. They are malleable, to form objects of different shapes by beating with a hammer. For example, it is because of the property of malleability of iron that an ironsmith can change the shape of a block of iron metal by hammering to make different iron objects such as an axe, a spade or a shovel, etc.
(ii) Non-Metals are Not Malleable. Non-Metals are Brittle. This means that non-metals cannot be beaten into thin sheets with a hammer. Non-metals break into small pieces when hammered.
Carbon is a non-metal. Carbon is found in many forms such as charcoal, coke, graphite and diamond, etc. Coal is also mainly carbon. The pencil lead is a form of carbon called graphite (see Figure). If we take a piece of carbon (say, a pencil lead or charcoal) and beat it with a hammer, it will break into pieces. We cannot hammer carbon (without breaking) to obtain thin sheets of carbon. Thus, carbon is a non-metal which is not malleable. Carbon is brittle.
Sulphur is also a non-metal. If we hammer a piece of sulphur, it will break into smaller pieces. We cannot hammer sulphur to obtain thin sheets of sulphur. Thus, sulphur is a non-metal which is not malleable, it is brittle. From this discussion we conclude that we cannot obtain thin sheets by beating non-metals. When beaten with a hammer, solid non-metals break into pieces. The property due to which non-metals break on hammering is called brittleness. Brittleness is a characteristic property of solid non-metals.
(i) Metals are Ductile. This means that metals can be drawn (or stretched) into thin wires.
Most of the metals are ductile. Gold and silver are among the best ductile metals. Copper and aluminium metals are also very ductile and can be drawn into thin copper wires and aluminium wires (which are used as electric wires). Iron, magnesium, and tungsten metals are also quite ductile and can be drawn into wires. Iron wires are used for making wire gauzes. Magnesium wires are used in science experiments in the laboratory. And thin wires of tungsten metal are used for making the filaments of electric bulbs. The property which allows the metals to be drawn into wires is called ductility. Ductility is another characteristic property of metals. From the above discussion we conclude that: Generally, metals are malleable and ductile.
(ii) Non-Metals are Not Ductile. This means that non-metals cannot be drawn into wires. They easily snap on stretching.
For example, sulphur and phosphorus are non-metals and they are not ductile. When stretched, sulphur and phosphorus break into pieces and do not form wires. Thus, we cannot get wires from non-metals. From the above discussion we conclude that: Non-metals are neither malleable nor ductile. Non-metals are brittle.
(i) Metals are Good Conductors of Heat and Electricity. This means that metals allow heat and electricity to pass through them easily.
If we hold one end of a metal spoon (like an aluminium spoon) in hot water, then its other end becomes hot very soon. This is because the metal of spoon conducts heat (or carries heat) from one end to the other end quickly. And we say that the metal spoon is a good conductor of heat. Copper, silver, gold, aluminium and iron metals are good conductors of heat. Though all the metals are good conductors of heat, silver metal is the best conductor of heat.
Copper metal is a better conductor of heat than aluminium metal. The cooking utensils (like a frying pan, etc.) are made of metals because metals are good conductors of heat (see Figure). Being a good conductor of heat, the metallic bottom of cooking utensil transfers the heat of gas stove quickly to the food kept inside it. We cannot hold a hot metal pan directly because it will conduct the heat quickly to our hand causing burns. We have to hold a hot metal pan from its handle made of plastic or wood (because plastic and wood do not conduct heat).
Let us now show the conduction of electricity by metals. We take a cell, a torch bulb fitted in a holder and some connecting wires (copper wires) with crocodile clips, and connect them to make an electric circuit as shown in Figure.
Let us insert a piece of aluminium foil between the ends of crocodile clips A and B. We will see that the torch bulb lights up at once (see Figure). This means that aluminium foil allows electric current to pass through it. In other words, aluminium metal is a good conductor of electricity.
Let us now remove the aluminium foil and insert an iron nail between the two ends of crocodile clips A and B. The bulb will light up again showing that iron metal is also a good conductor of electricity.
The connecting wires used in making the circuit shown in Figure are made of copper metal. Since the copper connecting wires allow electric current to pass through them, therefore, copper metal is also a good conductor of electricity. From this activity we conclude that metals are good conductors of electricity. Copper wires are used in household electric wiring because copper metal is a very good conductor of electricity. Copper metal is a better conductor of electricity than aluminium. Silver metal is the best conductor of electricity.
(ii) Non-Metals are Poor Conductors of Heat and Electricity. This means that non-metals do not allow heat and electricity to pass through them.
For example, sulphur is a non-metal which does not conduct heat or electricity. Similarly, a piece of coal (which is mainly carbon non-metal) also does not conduct heat or electricity. Many of the non-metals are, in fact, very good insulators. There are, however, some exceptions. A form of the carbon element, diamond is a non-metal which is a good conductor of heat. And another form of carbon element, graphite is a non-metal which is a good conductor of electricity. Being a good conductor of electricity, graphite is used for making electrodes (as that in dry cells).
(i) Metals are Lustrous (or Shiny). This means that metals have a shiny appearance.
If we observe the freshly cut surfaces of metals, we will find that they have a shiny appearance. This is called metallic lustre (or chamak). The shiny appearance of metals makes them useful in making jewellery and decoration pieces. For example, gold and silver are used for making jewellery because they are bright and shiny.
(ii) Non-Metals are Not Lustrous. They are Dull. This means that non-metals are not shiny they are dull in appearance. For example, sulphur and phosphorus are solid non-metals which do not have lustre (or shine). They are dull in appearance. There is, however, one exception. Iodine is a non-metal having lustre (or chamak). Iodine has a shining surface like that of metals.
(i) Metals are Usually Strong. They have High Tensile Strength. This means that metals can hold large weights without snapping (without breaking).
For example, iron metal (in the form of steel) is very strong having a high tensile strength. Due to this iron metal is used in the construction of bridges, buildings, railway lines, girders, machines, vehicles and chains, etc. Though most of the metals are strong but some of the metals are not strong. For example, sodium and potassium metals are not strong. They have low tensile strength.
(ii) Non-Metals are Not Strong. They have Low Tensile Strength. This means that non-metals cannot hold large weights. They easily snap. For example, graphite is a non-metal which is not strong. It has a low tensile strength. So, when a large weight is placed on a graphite sheet, it gets snapped (breaks).
(i) Metals are Sonorous. This means that metals make a ringing sound when we strike them.
Sonorous means capable of producing a ringing sound. If we drop a metal coin or a metal utensil on the floor of our house, we hear a ringing sound. And when the clapper (or hammer) of an electric bell strikes the metal gong, even then a ringing sound is produced. So, the metal objects make a ringing sound when we drop them on a hard floor or strike them with a hard object. We say that the metals are sonorous (or capable of producing a ringing sound). Suppose we have two boxes, one box made of metal and the other box made of wood, which are similar in appearance. We can tell which box is made of metal by striking them with a small hammer. The box which produces a ringing sound on being struck by the hammer will be the one made of metal. Metal sheets are used for making bells (like the bicycle bells and temple bells). The use of inetals for making bells is based on their property of being sonorous.
(ii) Non-Metals are Not Sonorous. This means that solid non-metals do not make a ringing sound when we strike them. If we drop a piece of carbon (say, a piece of charcoal) or a lump of sulphur on the floor or strike them with a hammer, we do not hear any ringing sound. This means that carbon and sulphur non-metals are not sonorous. They are not capable of producing a ringing sound when struck.
(i) Metals are Generally Hard. This means that most of the metals cannot be cut easily.
Though most of the metals are hard but their hardness varies from one metal to another. For example, if we try to cut a thin sheet
of iron metal with a pair of scissors, we will find that it is very, very difficult to cut the sheet of iron. This is because iron metal is very hard. On the other hand, a thin sheet of aluminium metal can be cut easily by using scissors. This means that aluminium metal is less hard. There are, however, some exceptions to this property of hardness of metals. Sodium and potassium metals are soft and can be easily cut with a knife. For example, if we try to cut a lump of sodium metal with a dry knife, we will find that it can be easily cut into small pieces (just like wax). This shows that sodium metal is soft. Magnesium metal can also be cut easily.
(ii) Most of the Solid Non-Metals are Quite Soft. This means that most of the solid non-metals can be cut easily.
For example, sulphur and phosphorus are soft non-metals which can be easily cut into pieces with a knife. Only one non-metal, diamond, is very hard. In fact, diamond is the hardest natural substance known.
Comparison Between the Physical Properties of Metals and Non-Metals
We will now compare the physical properties of metals and non-metals in tabular form. These physical properties can be used to distinguish between metals and non-metals.
Differences in Physical Properties of Metals and Non-Metals
|1. Metals are malleable and ductile.||1. Non-metals are neither malleable nor ductile. They are brittle.|
|2. Metals are good conductors of heat and electricity.||2. Non-metals are poor conductors of heat and electricity (except graphite which is a good conductor of electricity).|
|3. Metals are lustrous (or shiny).||3. Non-metals are not lustrous (or shiny). They are dull.|
|4. Metals are strong. They have high tensile strength (except sodium and potassium which are not strong and have low tensile strength).||4. Non-metals are not strong. They have a low tensile strength.|
|5. Metals are sonorous. They make a ringing sound when struck.||5. Non-metals are not sonorous. They do not make a ringing sound when struck.|
|6. Metals are generally hard (except sodium and potassium which are soft metals).||6. Solid non-metals are quite soft (except diamond which is extremely hard).|
An element can be identified as being a metal or a non-metal by comparing its properties with the general properties of metals and non-metals. While doing so we should, however, keep the various exceptions to the general properties of metals and non-metals in mind. We will now answer one question based on metals and non-metals.
State two reasons for believing that copper is a metal and sulphur is a non-metal.
The two properties which tell us that copper is a metal and sulphur is a non-metal are given below.
|1. Copper is malleable and ductile. It can be hammered into thin sheets and drawn into wires.||1. Sulphur is neither malleable nor ductile. It is brittle. Sulphur breaks into pieces when hammered or stretched.|
|2. Copper is a good conductor of heat and electricity.||2. Sulphur is a poor conductor of heat and electricity.|