What is an Element?
An element is a substance that cannot be broken down into two or more simpler substances by any chemical method by the application of heat or light. For instance, on melting the piece of gold, it still melts and remains as the gold element. These substances are composed of a singular type of atoms, that is, they are monoatomic. Elements are considered to be the building blocks of matter. There are 118 elements that exist in total till now, 94 elements out of these occur in nature whereas the 24 left are prepared artificially.
Elements can occur in all three states in the matter, that is, solid, liquid or gaseous state. Elements are recognized using chemical symbols and formulae. Elements maintain their homogeneity. For instance, a piece of gold is made up of only gold atoms. Atom is the smallest unit forming elements. It dictates the properties of elements. Elements also possess sharp melting and boiling points.
Example: Hydrogen is an example of an element that cannot be split down into two or more substances.
Types of Elements
Elements occur in all three forms, that is, metals, non-metals and metalloids.
Most of the elements in the periodic table are metals. They form cations, that is positive ions and contain metallic bonds. Metals comprise of alkali metals, lanthanides as well as transition metals. Metals are rigid substances possessing a shiny lustrous body and acting as good conductors of heat and electricity. For instance, metal is considered to be a good conductor of electricity. These can be easily hammered to form sheets and drawn into wires. Therefore, the metals are both malleable and ductile. Metals are usually crystalline solids. Metals display high chemical reactivity.
Metals have a tendency of losing electrons easily. Metals easily form a lattice of positive ions surrounded altogether by a cloud of delocalised electrons. A metal may be a chemical element, for instance, iron; or an alloy, for instance stainless steel; or even a molecular compound, for instance, polymeric sulphur nitride.
Characteristics of Metals
- Possess metallic lustre
Exception: Mercury is a liquid at room temperature.
Exception: Zinc is non-malleable and non-ductile.
- Hard Solids
Exception: Alkali metals, lithium and potassium are soft metals that can easily be cut through a knife.
- Good conductors of heat and electricity
Exception: Caesium and gallium have low melting points, which melt on the palm itself. Mercury, lead, titanic are bad conductors of electricity. Bismuth is the poorest conductor of heat.
- Mostly are mono-atomic, that is, contain a single type of atoms
- Low density and low melting point
- Sonorous, producing a deep or ringing sound when struck with another hard object.
Copper, Iron, Sodium, Calcium, Iron nails etc.
Applications of Metals
- Farming: Planters, tractors
- Construction: Nails in lumber construction
- Transportation: Trains, trucks, cars.
- Computers and electronic devices: TV, radio and calculators
- Household items: Vacuum cleaners, pumps and water heaters.
- Electronic power appliances: Boilers.
Non-metals possess qualities differing from those of metals. Non-metals have a dull, coloured or colourless appearance. Non-metals are generally brittle and do not possess the properties of malleability and ductility. They usually generally lack all the characteristics of metals. At room temperature, most of the non-metals are gaseous in nature. Some of them may be solid. One of the non-metals, bromine is liquid at room temperature. Majority of the non-metals have a dull appearance, except iodine. There are certain non-metals that can occur in different forms, called allotropes. For example, carbon.
Diamond is one of the allotropes of carbon. It has very high melting and boiling point and is the hardest naturally occurring substance. Non-metals are generally less dense in comparison to metals. Non-metals are the category of elements that form anions, that is negative ions by accepting or gaining electrons. This is because non-metals possess 4, 5, 6 or 7 electrons in their outermost shell which makes it easy to gain electrons during chemical reactions.
Characteristics of Non-Metals
Exception: Graphite possess lusture.
- Bad conductors of heat and electricity
Exception: Graphite is a good conductor of heat and electricity.
Exception: Carbon fibre is ductile but not malleable.
- Contains dual kind of atoms
- May be solid, liquids or gases.
- Non-Sonorous does not produce a deep or ringing sound when struck with another hard object.
Non-metals may be solid in nature: Carbon, Silicon, Phosphorus etc.
Non-metals may be liquid in nature: Bromine
Non-metals may also be gaseous in nature: Hydrogen, Chlorine etc.
Applications of Non-Metals
- Fertilizers: Hydrogen, Nitrogen, Ammonia, Nitric Acid
- Sports and music equipment
- Purification of water: Chlorine
- Sulphuric acid is prepared using sulphur.
- Hydrogen is used as rocket fuel.
The metalloids are basically the elements possessing intermediate in their properties between metals and nonmetals. They mostly act like non-metals in their physical properties. However, there are certain exceptions. For instance, metalloids are good conductors of electricity. Some of the metalloids contract when they are melted. They also possess a metallic and dull appearance. Boron, germanium, arsenic and antimony are some commonly known metalloids.
Characteristics of Metalloids
- Metalloids possess intermediate properties between metals and non-metals.
- Generally occur in solid-state.
- They are semi-conductive in nature.
- Contain one kind of atom.
Boron, Germanium, Antimony, Arsenic, Bismuth, Silicon, etc.
- Creation of alloys.
- Fluorescent lamps and infrared detectors: Germanium
- Computer chips as it is a semiconductor: Silicon
- Paints and ceramic enamels: Antimony
- Insecticide and in the preservation of wood: Arsenic
- Biological agents
Comparison in Metal, Non-Metals and Metalloids
|Metallic properties||Possess the highest degree of metallic behaviour.||Possess metallic behaviour.||Possess the metallic properties partially.|
|Location on periodic table||Left||Right||Between metals and non-metals.|
|Blocks||Located in s, p, d, f, blocks.||Located in s and p blocks.||Located in p block.|
|Appearance||Lustrous||Possess dull appearance.||Possess both dull or metallic appearance.|
|Electro-negativity||Low electronegativity.||High electronegativity.||Neither too high nor too low.|
|Conductivity||High thermal and electrical conductivity.||Low thermal and electrical conductivity.||Good thermal and electrical conductivity but less than metals.|
Question 1: What happens on smashing a piece of iron?
Since elements are not affected by any physical or chemical processes, therefore, on breaking the piece of iron it still remains a piece of iron.
Question 2: Explain the difference between Elements and Compounds?
Elements Compounds Consist of only one kind of atom. Consist of more than one kind of atom. Cannot be divided into two or more simpler substances by any physical or chemical means. Can be divided into elements by chemical means. There are only 118 types of elements known to mankind. Unlimited number of compounds exist
Question 3: Illustrate an example of a metal and a non-metal which are liquids at room temperature.
Mercury is the metal and bromine the non-metal which is liquid at room temperature respectively.
Question 4: Why copper is a metal and sulphur is a non-metal.
(i) Copper is malleable and ductile whereas sulphur is neither malleable nor ductile.
(ii) Copper is a good conductor of heat and electricity whereas sulphur is a poor conductor of heat.
Question 5: Why is polonium a lesser-known non-metal?
Polonium is a highly reactive non-metal. It possesses radio-active properties and is highly toxic in nature.
Question 6: Why are :
(a) School bells made of metals.
(b) Electric wires made of copper.
(a) Since, metals are sonorous, i.e. they produce a sharp ringing sound when struck with any hard material.
(b) Copper conducts heat and electricity highly efficiently, that is it possess a very high melting point.
Question 7: Why are platinum, gold and silver preferred elements to make jewellery?
Platinum, gold and silver and situated at the bottom end of the reactivity series, thereby possessing very less reactivity. They do not chemically react with air and water. Because of this reason, they are termed as noble metals. Also, they possess a bright lustre, therefore, suitable for making ornaments.