TNPSC Chemistry - Elements
ELEMENTS:
Pure substance: A pure substance has fixed composition and fixed properties which cannot be easily separated by physical methods.
One can recognise a pure substance by its properties such as melting point,boiling point,density, refractive index, electrical conductivity and viscosity.
For example, pure water boils at 100゜ Celsius at one atmospheric pressure and ice freezes at o゜ Celsius. These are the properties of all samples of pure water,regardless of their origin.
In Science a pure substance is either an element.
Let us see the different views of an element put forth by scientists
⭐BOYLE:
An element is a pure substance that cannot be split into anything simple by physical or chemical method.
⭐LAVOISIER:
An element is the basic form of matter that cannot be broken into a simpler substance.
⭐ MODERN ATOMIC THEORY:
An element is made of same kind of atoms.
There are 118 elements known at present
92 elements occur in nature.
26 elements prepared in laboratory by artificial methods.
112 elements have been authenticated by IUPAC(International Union of Pure and Applied Chemistry),and are allotted symbols.
In earth's crust, Oxygen is the most abundant element followed by silicon.
About 99% of the mass of human body is made up of six elements (Oxygen -65%, Carbon -18%, Hydrogen -10%, Nitrogen -3%, Calcium -2%) and the rest 1% by other elements.
Hydrogen and helium are the main elements in the universe and stars.
CLASSIFICATION OF ELEMENTS BASED ON THEIR PHYSICAL STATE:
LIQUIDS:
Mercury, bromine(at room temperature) cesium and gallium can exist in liquids around 30゜ Celsius.
GASES:
Hydrogen, nitrogen, Oxygen, chlorine, fluorine, helium, neon, argon, Krypton, radon and xenon.
SOLIDS:
Remaining elements are solids. e.g. Carbon,silicon,copper,gold etc.
CLASSIFICATION OF ELEMENTS BASED ON PROPERTIES:
METALS:
Out of the 92 natural elements 70 elements are metals.
Metals are♦ Hard lustrous(shining in appearance),
♦ Malleable(can be beaten into very thin sheet),
♦ Ductile(drawn into wire),
♦Good conductors of heat and electricity,
♦Sonorous(producing sound)
e.g. Copper,gold,silver, iron etc,.
NON - METALS:
Only about 16-17 elements are non- metals.
Non - metals are :♦Soft,
♦Non lustrous,
♦Non- malleable,
♦Non- ductile,
♦Bad conductors of heat and electricity,
♦Non- sonorous.
e.g. Hydrogen, oxygon, sulphur, carbon etc,.
METALLOIDS:
Very few semi-metals are known as METALLOIDS which shows properties of metals as well as non-metals.
e.g. Boron, silicon, germanium etc,.
USES OF SOME ELEMENTS:
♣ LED - Gallium.
♣ LCD - Indium.
♣ X -ray diagnosis - Barium.
♣ MRI diagnosis - Gadolinium.
♣ Atomic clocks - cesium.
♣ Luminous watches - Radium.
♣ Radioactive diagnosis - Technetium.
♣ Thermoelectric coolers - Tellurium.
♣ Photography film - Bromine.
♣ Disinfectant - Iodine.
♣ Earthmover - Manganese.
Pure substance: A pure substance has fixed composition and fixed properties which cannot be easily separated by physical methods.
One can recognise a pure substance by its properties such as melting point,boiling point,density, refractive index, electrical conductivity and viscosity.
For example, pure water boils at 100゜ Celsius at one atmospheric pressure and ice freezes at o゜ Celsius. These are the properties of all samples of pure water,regardless of their origin.
In Science a pure substance is either an element.
Let us see the different views of an element put forth by scientists
⭐BOYLE:
An element is a pure substance that cannot be split into anything simple by physical or chemical method.
⭐LAVOISIER:
An element is the basic form of matter that cannot be broken into a simpler substance.
⭐ MODERN ATOMIC THEORY:
An element is made of same kind of atoms.
There are 118 elements known at present
92 elements occur in nature.
26 elements prepared in laboratory by artificial methods.
112 elements have been authenticated by IUPAC(International Union of Pure and Applied Chemistry),and are allotted symbols.
In earth's crust, Oxygen is the most abundant element followed by silicon.
About 99% of the mass of human body is made up of six elements (Oxygen -65%, Carbon -18%, Hydrogen -10%, Nitrogen -3%, Calcium -2%) and the rest 1% by other elements.
Hydrogen and helium are the main elements in the universe and stars.
CLASSIFICATION OF ELEMENTS BASED ON THEIR PHYSICAL STATE:
LIQUIDS:
Mercury, bromine(at room temperature) cesium and gallium can exist in liquids around 30゜ Celsius.
GASES:
Hydrogen, nitrogen, Oxygen, chlorine, fluorine, helium, neon, argon, Krypton, radon and xenon.
SOLIDS:
Remaining elements are solids. e.g. Carbon,silicon,copper,gold etc.
CLASSIFICATION OF ELEMENTS BASED ON PROPERTIES:
METALS:
Out of the 92 natural elements 70 elements are metals.
Metals are♦ Hard lustrous(shining in appearance),
♦ Malleable(can be beaten into very thin sheet),
♦ Ductile(drawn into wire),
♦Good conductors of heat and electricity,
♦Sonorous(producing sound)
e.g. Copper,gold,silver, iron etc,.
NON - METALS:
Only about 16-17 elements are non- metals.
Non - metals are :♦Soft,
♦Non lustrous,
♦Non- malleable,
♦Non- ductile,
♦Bad conductors of heat and electricity,
♦Non- sonorous.
e.g. Hydrogen, oxygon, sulphur, carbon etc,.
METALLOIDS:
Very few semi-metals are known as METALLOIDS which shows properties of metals as well as non-metals.
e.g. Boron, silicon, germanium etc,.
USES OF SOME ELEMENTS:
♣ LED - Gallium.
♣ LCD - Indium.
♣ X -ray diagnosis - Barium.
♣ MRI diagnosis - Gadolinium.
♣ Atomic clocks - cesium.
♣ Luminous watches - Radium.
♣ Radioactive diagnosis - Technetium.
♣ Thermoelectric coolers - Tellurium.
♣ Photography film - Bromine.
♣ Disinfectant - Iodine.
♣ Earthmover - Manganese.
You may search for our products through the search bar on our website. If you would like to receive a copy of our product catalog, please contact us at info@alfa-chemistry.com. Vat Orange 2
பதிலளிநீக்கு