INTRODUCTION
Elements are the basic components of all matter. An element is a substance that cannot be broken down into simpler substances through ordinary chemical processes. Many familiar names like copper, silver, gold, oxygen, nitrogen, carbon, and sodium, all are elements. The building block of elements is an atom and each atom has a specific symbol. For example, nitrogen is designated symbol ‘N’, oxygen by symbol ‘O’ and copper by symbol ‘Cu’. Based on the different properties, elements are classified as metals and non-metals.
METALS
They occur in nature in various forms, so their reactivities also differ greatly. Almost all are found in the earth's crust, while a few are also found in seawater as salts. Aluminium is the most abundant metal on earth. Metals that do not react with oxygen, moisture, carbon dioxide, and other chemicals are found in the free state. Gold, silver, and platinum are found in their native state due to their less reactivity. Metals with high reactivity, such as potassium, sodium, aluminium, and zinc exist in the form of oxides, sulphides, and carbides. Apart from mercury (which is liquid), all other metals are solids. All the metals have high densities. Elements or compounds that occur naturally in the earth’s crust are known as minerals. Minerals contain metals in the combined state e.g., hematite which contains iron as metals, and calcium carbonate contains calcium. Metals can be suitably mined from minerals and these minerals are known as ores. The process of extracting pure metals from their ore is known as metallurgy.
NON-METALS
They are mostly found in their free state in the atmosphere. Non- metals can be solid, liquid, and gases at room temperature. Some examples of non-metals are hydrogen, carbon, sulphur, oxygen, chlorine, and nitrogen. Hydrogen is the most abundant non-metals found in the universe. Non-metals also exist in the form of compounds, e.g., carbon exists as graphite, diamond, and fullerenes.
Noble gases are examples of those non-metals which occur in a free state. Few non-metals likewise occur in the combined state in nature. For instance, hydrogen and oxygen occur in the combined state in water. Similarly, sulphur exists in the free state and the combined state as sulphides (S2-) and sulphates (SO42-).
METALLOIDS
The elements that have few properties of metals and non-metals are called metalloids. We can say that the elements whose properties are intermediate between those of metals and non-metals are known as metalloids. Boron, silicon, germanium, and arsenic are a few examples of metalloids. Metals are good conductors of electricity while non-metals do not conduct electricity but metalloids conduct electricity to a small amount. The most abundant metalloid present on earth’s crust is silicon.
PHYSICAL PROPERTIES OF METALS AND NON-METALS
1. Hardness and Luster
Metals like silver, gold, aluminium, are hard and lustrous. They have lustre or a shining appearance which makes them suitable for the production of jewellery and decorative items. Gold and silver are examples of metals that are used for making jewellery.
Non-metals are not shiny; they are dull in appearance. For example, sulphur and phosphorus are solid non-metals with no lustre. Non-metals like carbon present in pencil lead are not hard and look dull. Diamond and iodine are exceptional non-metals that have lustre characteristics.
2. Malleability
Malleability is the physical property of metals by which they can be beaten to thin sheets. Aluminium, copper, silver, gold, etc. are the most malleable metals that are known. Silver and aluminium metals can be beaten into thin foils due to this property.
Non-metals are non-malleable. They are brittle and break into small pieces when hammered. That’s why they cannot be beaten into sheets or foil.
3. Conductor of Heat and Electricity
Metals are good conductors of heat and electricity. Silver metal is the best conductor of heat and electricity. Copper is generally used in electrical appliances and household wirings due to its high electrical conductivity. Lead and mercury are the metals that are poor conductors of heat.
In general, non-metals are poor conductors of heat, but diamond is an exception due to its high heat conductivity even as a non-metal.
4. Ductile
Metals can be drawn into wires; this property is known as ductility. Copper and silver wires are common examples. We can’t draw mercury into wires because it exists in a liquid state. Thin wires of tungsten metal are used for making the filaments of electric bulbs.
Non-metals cannot be drawn into wires as they are not ductile. They will shatter. As an example, phosphorus and sulphur are non-metals that do not exhibit ductility. When they are stretched, they break into pieces hence they do not form wires.
5. Sonorous
When metals strike with each other, produce sound. This property is known as sonorous. The ringing of bells and drinking of coins prove that metals are sonorous. Some examples are iron, aluminium, tin, etc.
Non-metals are non-sonorous and produce a very dull sound when struck with a hard object.
6. Melting and boiling points
Generally, metals have high melting and boiling points. For example, the melting point of copper is 1085˚C and its boiling point is 2562 ˚C. metals such as tungsten, platinum, iron have high melting and boiling points whereas mercury, francium, cesium, gallium have very low melting points.
Most of the non-metals have low melting and boiling points. The chemical element with the lowest melting point is helium and the element which has the highest melting point is carbon in the form of a diamond which has a melting point of 3723 ˚C.
DIFFERENCE BETWEEN METALS AND NON-METALS:
CHEMICAL PROPERTIES OF METALS AND NON-METALS
Metals and non-metals show different chemical properties. They react to different extent with air, water, and acids. For instance, sodium reacts with cold water or air while iron does not immediately react with cold water. This is because of the high reactivity of sodium in comparison to iron. Let’s discuss some of the important chemical properties of metals and non-metals.
A) Reaction of metals with oxygen
Metals combine with oxygen to form metal oxides which are basic in nature. The general equation for the formation of the metal oxide is as follows:
Metal + Oxygen → Metal oxide
Different metals have different reactivities towards oxygen and they react at different temperatures too. Sodium and potassium are the most reactive metals. They burn in the presence of air and give their corresponding oxides at room temperature. Sodium metal reacts with moisture present in air so it is always kept in kerosene oil.
(a) Sodium metal reacts with oxygen to form sodium oxide.
(b) Copper reacts with oxygen to form copper (II) oxide, a black oxide.
(c) Magnesium metals burn in the air, it combines with oxygen of the air to form magnesium oxide (a basic oxide):
(d) Iron, in the presence of moist air, slowly oxidises to produce iron oxide (rust).
Corrosion
The process of slow destruction or damage of metals due to attack of atmospheric gases and moisture on its exterior. Rusting is an example of the corrosion of iron. It is a process where iron reacts with air and moisture and a reddish-brown flaky substance is formed on its surface. This reddish-brown surface is known as rust.
Similarly, when copper metal is exposed to moist air for a long time, then copper reacts with water, carbon dioxide, and oxygen present in the air to form a green coating on the copper metal.
Thus, when a copper object is exposed to moist air for a long time, a green coating is developed on its surface. If we make a suspension of a little green coating in water and test it with litmus paper, we will find that it turns red litmus paper to blue. This shows that the green coating formed on the copper object is basic.
Reaction of non-metals with oxygen
Non-metals such as carbon, sulphur, and phosphorus when exposed to heat in the presence of oxygen, form their corresponding oxides. These oxides are acidic as they form acids when they are dissolved in water. Thus, they turn blue litmus to red. Hence non-metallic oxides are called acidic oxides.
(a) Carbon when strongly heated in the presence of air, it reacts with oxygen to form carbon dioxide. When this carbon dioxide is dissolved in water, it forms carbonic acid which turns blue litmus red.
(b) When sulphur burns in the air on gentle heating, it forms a gas which is sulphur dioxide, a pungent gas. This gas when dissolved in the water, leads to the formation of sulphurous acid.
B) Reaction with water
I) Reaction of metals with water
Most of the metals react with water to form metal hydroxide or metal oxide and hydrogen gas. The liberated hydrogen gas burns with a pop sound. Some metals react vigorously even with cold water, some metals react with hot water, while a few of them react with steam whereas some metals do not react with steam.
Metals such as sodium and potassium, which are very highly reactive, react vigorously with cold water to form hydroxides and hydrogen gas. Magnesium is a less reactive metal so it reacts very slowly with cold water, while it reacts rapidly with hot water. Sodium reacts violently with cold water to produce sodium hydroxide and hydrogen gas. A large amount of heat is evolved in this reaction, which results in hydrogen catching fire.
Calcium reacts with cold water; this reaction is not as vigorous as that of sodium because the heat released is insufficient for hydrogen to catch fire. Metals such as gold, silver, lead, and copper do not react at all with water.
II) Reaction of non-metals with water
Non-metals usually do not react with water. Though oxygen dissolved in water but to a very less extent. This oxygen behaviour is crucial for aquatic living organisms as their lives depend on the oxygen dissolved in the water. Chlorine is the other non-metals that dissolve in the water to form an acidic solution.
C) Reaction with acids
I) Reaction of metals with acids
The reaction of an acid with metals leads to the formation of salt and hydrogen gas.
Less reactive metals such as copper, silver, and gold do not react with dilute acids. Different metals react based on their reactivity tendency. Some metals react explosively with dilute acids, some metals react rapidly with dilute acids, few of them react with dilute acid only upon heating whereas some metals do not react with dilute acids at all.
Magnesium metal reacts with dilute hydrochloric acid to form magnesium chloride and hydrogen gas. The reaction is given below:
Aluminium, zinc, iron metals also react with dilute acids to form the corresponding metal chlorides and hydrogen gas. Aluminium reacts with hydrochloric acid to form aluminium chloride and hydrogen gas.
II) Reaction of non-metals with acids
Non-metals do not react with dilute acids to form salts and hydrogen gas. For instance, if we take charcoal or sulphur powder in a test tube and add dilute hydrochloric acid, then no reaction takes place even on heating. This experiment demonstrates that the non-metals do not react with acids and hence no hydrogen is liberated. Few non-metals react with hot and concentrated sulphuric acid and nitric acid but no hydrogen gas is produced in this reaction too.
D) Reaction with bases
I) Reaction of metals with bases
Some metals react with bases to form salts and hydrogen gas.
Zinc reacts with a concentrated sodium hydroxide base to form salt and hydrogen gas. The reaction is as given below:
Aluminium is heated with sodium hydroxide; sodium aluminate and hydrogen gas are formed.
Only a few metals react with sodium hydroxide to form hydrogen gas, all the metals do not react with bases to produce hydrogen gas.
II) Reaction of non-metals with bases
Only a few non-metals react with bases such as sodium hydroxide but they do not produce hydrogen gas. The reactions of non-metals with bases are very complex. For instance, when phosphorus dissolves in sodium hydroxide, phosphine is liberated and the formation of sodium hypophosphite.
Reactivity of metals
All the metals do not show the same reactivity. The tendency of any metal to react with other substances to form compounds is known as the reactivity of metals. Based on their reactions with oxygen, water, and acids as well as displacement reactions, the metals can be arranged in a series according to their chemical reactivities. Less reactive metals occur in the earth’s crust in the native state i.e., elemental state, while the high reactive metals occur in the form of compounds. The arrangement of metals in a vertical column in order of decreasing reactivities is known as the reactivity series of the metals. It is also known as the activity series of metals. In this series, the most reactive metal is placed on the top whereas the least reactive metal is placed at the bottom.
It is to be noted that potassium is the most reactive metal, so it is placed at the top of the series. As we move down in the series, the chemical reactivity of metals decreases steadily. Gold being the less reactive metal of the series has been placed in the bottom. We have discussed the metal reactivity series here as it will help us in understanding the displacement reaction of metals.
Displacement reactions
A more reactive metal tends to replace the less reactive metals from its salt solution. Such reactions are called displacement reactions. When we put a more reactive metal into the solution of less reactive metal, then the more reactive metals displace the less reactive metal from its salt solution. The more reactive metal becomes part of the salt whereas the less reactive metal gets free. Let us see some examples to make this point clear.
(a) Reaction of iron metal with copper sulphate solution:
When a strip of iron metal is dipped into copper sulphate solution for some time, then the blue colour of the solution diminishes and a red-brown coating of copper metal is deposited on the iron strip.
In this case, the solution gets converted into greenish due to the formation of ferrous sulphate. We know that iron metal is more reactive than copper metal. Hence in this reaction, a more reactive metal is displacing a less reactive metal from its salt solution.
Now if we take the reverse case where a copper strip gets dipped into the ferrous sulphate solution, a less reactive metal cannot displace a more reactive metal from its salt solution. Hence no displacement reaction takes place.
(b) Reaction of zinc metal with copper sulphate solution:
When a zinc metal strip is placed in copper sulphate solution for some time, the blue color of the copper sulphate solution diminishes gradually, and red-brown copper metal is deposited on the zinc strip. The reaction can be written as follow:
In this reaction, a more reactive metal ‘zinc’ is displacing a less reactive metal ‘copper’ from its salt solution. The blue colour of the solution gradually becomes colourless due to the formation of zinc sulphate solution. The copper metal is deposited on the zinc strip as the red-brown coating. So, in this displacement reaction, zinc metal displaces copper metal from copper sulphate solution. This reaction takes place only because zinc is more reactive than copper. On the other hand, if copper is added to a zinc sulphate solution, no reaction will take place.
This reaction does not take place because copper metal is less reactive than zinc metal, a less reactive metal ‘copper’ cannot displace a more reactive metal ‘zinc’ from its salt solution, zinc sulphate solution. Thus, copper cannot displace zinc from zinc sulphate solution.
(c) Reaction of zinc metal with ferrous sulphate solution:
When a strip of zinc metals is placed into the ferrous sulphate solution, then the following reaction occurs:
In this reaction, zinc metal displaces iron metal from ferrous sulphate solution. This displacement reaction takes place only because of the reason that zinc metal is more reactive than iron. If we take the reverse case where an iron strip is placed into the zinc sulphate solution, no displacement reaction occurs.
COMPARISON OF CHEMICAL PROPERTIES OF METALS AND NON-METALS
We will now compare the chemical properties of metals and non-metals in the below table.
NOBLE METALS:
The least reactive metals such as gold and platinum are called noble metals. They do not react with water, air, acids, bases, and most of the other substances. These metals are chemically inert and hence do not undergo corrosion and can maintain their lustrous surfaces for a long extent.
USES OF METALS
Our daily lives have been made easier by the use of metals. Metals are used in making nails, screws, water boilers, office furniture, aeroplanes, trains, satellites, and many more things. A few of the important uses of metals have been given below.
Iron, copper, and aluminium are used in the making of cooking utensils.
Iron is used in making cutter machines, axe heavy machinery, automobiles, gates, windows, stoves, pipes, railway tracks, nuts, gas cylinders, water tanks, and bolts.
Aluminium foil is used for making electric wires for household wiring, electric motors, and many more electrical parts. For its lightweight, it is used in making aircraft bodies. The aluminium foil papers used to pack food at your home are made from aluminium.
Copper is widely used for making cooking vessels, electric cables, and other electrical goods. It is also used in the integrated circuits and making of electromagnets.
Lead is used in making paints and car batteries.
Zinc is used for galvanising iron to protect it from rusting. It is also used in die castings which are essential in automobiles and other industries.
Chromium and nickel are used to electroplate various objects and make stainless steel.
Gold, platinum, and silver are used to make jewellery.
USES OF NON-METALS
Nitrogen is used in the making of fertilisers. Liquid nitrogen is used in various things such as refrigerants and medicines. Nitrogen is also filled in the chips packet to prevent the rancidity of the food items.
Oxygen is stored in cylinders that are used by hospitals and mountaineers. The steel industries use these non-metals for removing unwanted compounds in the steel.
Graphite is used for making black lead pencils. It is used for making electrodes and crucibles for laboratory use. It is also used as a lubricant in machinery and for making fuel rods in nuclear reactors.
Sulphur is used in the vulcanization of rubber, which makes rubber hard enough to be used in tyres of vehicles.
ALLOYS
An alloy is a homogenous mixture of two or more metals or metals and non-metals. The goal of making metal alloys is to enhance some special properties of the metals. It is usually made by mixing metals in a definite proportion in their molten state. Few metals have been given in the below table.
SUMMARY
Metals are generally hard, strong, solids. They are lustrous, sonorous, malleable, ductile, and good conductors of electricity and heat.
Most non-metals are solid or gaseous, brittle, soft, and poor conductors of heat and electricity.
Most metals combine with oxygen to form metallic oxides while non-metals form non-metallic oxides.
Most metals react with water to produce a metal hydroxide or metal oxide and hydrogen gas. Non-metals do not react with water.
Metals are arranged in the decreasing order of activity in the activity/reactivity series. This series helps us to understand the chemical behaviours of metals.
Metals react with acids to produce salts and hydrogen gas. Non-metals do not react with acids.
Most metals do not react with bases.
In displacement reactions, a metal reacts with a salt solution and displaces the metal present in it.
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