In this universe, there are millions of substances, but we know all these substances are made up of a limited no. of materials. They are called elements. Now, these elements are also classified into three categories – Metals, Non-Metals and Metalloids.
Elements are broadly classified into two categories – Metals & Non-Metals based on the physical and chemical properties shown by them. But there were some elements found that show both the properties of metals and non-metals. They were called Metalloids.
Physical properties of Metals
Metals show some properties that can be observed physically without changing the chemical composition of the metals. These properties are shown below:
- State- Metals are hard and crystalline solids (except mercury – which is a liquid)
- Metallic Lustre- Metals in their pure state shine. This property is called metallic lustre. In other words, they shine when they are polished.
- Density- Metals have a high density (except sodium, potassium and lithium)
- Hardness- Almost all the metals are hard solids except sodium and potassium which can be cut through a knife.
- Melting and Boiling Points- Metals usually have high melting and boiling points
- Malleability- Malleability means that they can be hammered or beaten to sheets. Most of the metals are malleable. Gold, silver, copper are highly malleable. (Exception – Zinc is brittle)
- Sonority- Metals when struck by a hard object they produce a sound. This property is called sonority.
- Thermal and electrical conductivity- Metals are good conductors of heat and electricity.
- Solubility- Metals are either soluble in water or in organic solvents like toluene.
- Tensile Strength- All metals except zinc has high tensile strength.
- Ductility- Metals are highly ductile
Now, having discussed the physical properties of metals, let’s now discuss the chemical properties of metals
Chemical properties of Metals
Chemical properties are the characteristics shown by a substance when it undergoes chemical reactions. Following are some chemical properties of Metals
- Electronic Configuration- Metals have either 1, 2 or 3 electrons in their valence shell in their electronic configuration.
- Valency- Metals have +1, +2 or +3 valency.
K – 1e- –> K+
Na -1e- –> Na+
- Formation of Ions- Metals loses electrons during a chemical reaction and form positively charged ions called cations.
- Reducing Nature- Metals are good reducing agents since they lose electrons.
- Reaction with oxygen and the nature of the oxide- Metals reacts with oxygen to form their respective oxides. These oxides are basic in nature. There are some oxides that are also soluble in water. They are called alkali.
Metal +Oxygen → Metal Oxide (Heat) (basic)
4Na + O2 → 2Na2O
4Cu + O2 → 2Cu2O
Some important points:
- Very reactive metals like sodium, potassium and calcium react vigorously with water to form their respective oxides without the need for heat. These metallic oxides formed are soluble in water and forms soluble hydroxides. They are called alkalis.
Na2O+ H2O → 2NaOH
K2O +H2O → 2KOH
- Metals like zinc, aluminium and lead form amphoteric oxides. Amphoteric Oxides are those oxides that react both with acid and base to produce salt and water.
- Metals like gold and silver do not produce their oxide with oxygen even on heating it.
- Reaction with water- Metals react with water to form their respective hydroxides along with the release of hydrogen gas. Depending upon their reactivity, some very reactive metals like sodium and calcium reacts with cold water while less reactive metals react with steam.
- Reactive metals like sodium and potassium react violently with cold water to form their respective hydroxides and hydrogen gas. Examples:
Metal + Water → Metallic Hydroxide + Hydrogen
2Na + 2H2O → 2NaOH + H2
2K + 2H2O → 2KOH + H2
Ca + 2H2O → Ca(OH)2 + H2
- Less reactive metals react with steam to produce their respective hydroxide.
- Noble metals like gold, silver, platinum do not react with water or steam.
- Reaction with acids- Metals above Hydrogen in reactivity series reacts with acids to form their respective salts and produces hydrogen. They perform a displacement reaction as they displace hydrogen from the acid.
Some important points:
- Reactive metals like sodium and potassium react vigorously with water releasing a tremendous amount of heat.
2Na + 2HCl → 2NaCl + H2
- Less reactive metals like magnesium, zinc reacts moderately with acids
Mg + 2HCl → MgCl2 + H2
Zn + 2HCl → ZnCl2 + H2
- Metals react with hydrochloric acid and sulfuric acid to produce salt and hydrogen but not with nitric acid. This is because nitric acid is a strong oxidizing agent, it readily oxidizes hydrogen to form water.
Physical properties of Non-Metals
Non-Metals show some properties that can be observed physically without changing the chemical composition of the metals. These properties are shown below:
- State- Non-Metals are either gases or liquids (Only exception is bromine which is liquid at room temperature)
- Metallic Lustre- Non-Metals have a dull look. They will not shine even if they are polished. (Only exception is Graphite and Iodine)
- Density- Non-Metals have a low density (Though there is an exception i.e Diamond which is highly dense)
- Hardness- Non-Metals are usually not hard. If solid they are also brittle in nature(breaks easily). Exception- Diamond is the hardest substance.
- Melting points and boiling points- Non-metals have low melting and boiling points.
- Malleability- Non-Metals are non-malleable. They are brittle in nature i.e they break down into powder when they are beaten.
- Sonority- Non-metals do not produce any sound when they are struck by a hard substance. They are not sonorous.
- Thermal and electrical conductivity- All non-metals are either a poor conductor or non-conductor of electricity except graphite and gas carbon which are good conductors of heat and electricity.
- Solubility- In the case of non-metals, there is no such fixed rule that applies to the solubility example Sulphur is insoluble in water while chlorine is highly soluble in water.
- Tensile Strength- Non- metals have low tensile strength except carbon fibre which have high tensile strength.
- Ductility- Non-metals metals are not so much ductile.
Now let’s understand the chemical properties of metals and non-metals
Chemical Properties of Non-Metals
Chemical properties are the characteristics shown by non-metals when they undergo chemical reactions. Following are some of the chemical properties of Non-metals:
- Electronic configuration- Non-metals have 5, 6 or 7 electrons in their valence shell in their electronic configuration. [Exception: Hydrogen which has only 1 electron but still a non-metal]
- Valency- Non-metals have -1, -2 or -3 valencies.
- Formation of Ions- Non-metals gains electrons during a chemical reaction and form negatively charged ions called anions.
- Reducing Nature- Non-metals are good oxidizing agents since they gain electrons.
- Reaction with oxygen and the nature of the oxide- Non-metals also reacts with oxygen to form their respective oxides. These oxides are acidic in nature.
Non-Metal + Oxygen → Non-Metallic oxide
Some important points:
- Non-metals oxides react with water to form acids.
Example: CO2 + H2O → H2CO3
SO2 + H2O →H2SO4
- Hydrogen burns in oxygen to form water.
H +O2 →H2O
- Metal oxide reacts with water to form acids.
Example: CO2 + H2O(l) →H2CO3
- Reaction with water- Non-metals do not react with water except chlorine which forms chlorine water and hydrochloric acid.
- Reaction with acids- Non-metals do not react with dilute acids, but they react with concentrated acids.
C + H2SO4 → CO2 + SO2 + H2O
S + 2H2SO4 → 3SO2 + 2H2O
S + HNO3 → SO2 + NO2 + H2O
Now, having understood the metals and non-metals and seen the difference between the physical and chemical properties of metals and non-metals, let’s now understand metalloids.
Metalloids are a very small group of elements that have some properties (both physical and chemical) similar to both metals and non-metals. Some examples of metalloids are Silicon, Germanium, boron etc.
Some general properties of Metalloids
- They are brittle in nature
- They have a lustrous appearance like metals and are solids at ambient temperatures.
- They have energy bands like semiconductors.
- They are usually moderate conductors of electricity.
- They usually form amphoteric or weakly acidic oxides with oxygen.
- They have intermediate(can also be called moderate) values of ionization potential and electronegativity in comparison to metals and non-metals.
- They generally have 3 to 6 electrons in their valence shell (or outermost shell).
- They can be used to make alloys.
Uses of Metalloids
- Silicon and germanium are the main raw materials used in making digital components like diodes, silicon chips etc.
- Elements like antimony are used in many alloys.
- They can also be used as catalysts in many reactions.
Question 1. Name a hard Non-Metal.
Diamond although being a non-metal is the hardest substance.
Question 2. Name two metals that are liquid at room temperature.
Mercury and Gallium are two metals that are liquid at room temperature.
Question 3. What property helps gold and silver to be used as jewellery?
Gold and silver are hard and highly malleable, therefore, they can be made into fine sheets and different shapes without breaking them, thus, they are used in making jewelries of different shapes.
Question 4. State the properties of copper that facilitates it to be used as an electrical wire.
The two properties of copper that make it to be used as an electrical wire:
- Copper is highly ductile, thus can be easily drawn into wires.
- Copper, being a metal, is a good conductor of electricity, thus it easily allows electric current to pass through them.
Question 5. Name the metals that form amphoteric oxides on reaction with oxygen.
Zinc, aluminium and lead form amphoteric oxides on reacting with oxygen.
Question 6. Name the non-metal that has a shine.
Graphite is a non-metal that has shine.
Question 7. Differentiate between metals and non-metals on the basis of:
- Conductivity of electricity
|Metals are generally hard solids except zinc which is brittle
|Non-Metals are brittle in nature and easily break down.
|Metals are highly malleable.
|Non-metals are not malleable.
|Conductivity of Electricity
|Metals are very good conductors of electricity
|Non-metals are generally poor conductors of electricity.
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