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Thursday, 2 April 2020

Facts about Chemical Elements

Facts about Chemical Elements



The most common element in the atmosphere - Nitrogen.

Silicon is the second most abundant element in the earth crust.

Elements having more electronegative values are good oxidising agents.

The element having maximum electro negativity is Fluorine (4.0), next to it is Oxygen (3.5). Nitrogen and Chlorine have almost same electro negativity (3.0).

Most electropositive element is Francium. But it is not stable, it is radioactive.

Caesium is the most electropositive stable element and has lowest ionisation energy and is therefore largely used in photoelectric cells.

The tenth most abundant element in the earth crust is phosphorus.

White phosphorus is the most reactive form of phosphorus.

Red phosphorus is more stable than white phosphorus.

White phosphorus is a strong poison. As it bums itself in the air it is preserved under water.

Red phosphorus is non-poisonous. It is used in the manufacture of match boxes.

Major elements present in sea-water are chlorine, sodium, magnesium, sulphur, calcium, potassium, carbon etc.

The radioactive liquid element - Francium.

The radioactive gaseous element - Radon.

The element which shows highest electron affinity - Chlorine.

The densest element - Osmium.

The heaviest gaseous element - Radon.

Most stable element - Lead.

The first man made element - Technetium.

Element & Disease

1. Mercury - Minamatha
2. Cadmium - Ethai-ethai
3. Lead - Plumbism
4. Silicon – Silicosis
5. Fluorine - Fluorosis
6. Copper - Wilson's

 The halogens extracted from sea-water are chlorine and bromine.

 The element with highest melting point is Carbon (Diamond) about 4000K.

 The metal with highest melting point is Tungsten (3422°C or 3695K).

 The most reactive element - Fluorine.

 The most complex element available from earth is Uranium - 238.

 The natural element having highest atomic weight is Uranium.

 TEL is added to petrol as an octane booster to prevent knocking.

 Lithium is kept by covering with paraffin wax.

 Mercury is generally used as a thermometric fluid.

 Eka-aluminium and eka-silicon are Gallium and Germanium.

 Astatine is the radio active halogen.

 Chlorine is used in the manufacture of insecticides.

 Iodine is obtained from sea weeds. Iodine sub-limes on heating.

 Explosives generally contain nitrogen.

 Tungsten has the highest melting point of all the metals. Hence, it is used for filaments in electric bulbs.

 Caesium is used in atomic clocks.

 The element which is used to coat the photo-copying drum of Xerox is selenium.

 Silicon and Germanium are used in the manufacture of transistors and IC chips due to their semi conductivity.

Important Elements

Hydrogen

The most abundant element in the universe - hydrogen.

It is the third most abundant element in the surface of globe.

Hydrogen is the 9th most abundant element in earth's crust.

Hydrogen was discovered by Henry Cavandish (1766) and its name hydrogen was given by Lavoisier.

First element in the periodic table.

Hydrogen is produced commercially from water, mainly by the Bosch Process.

Pure hydrogen is a colourless gas without any smell or taste.

It has the lowest density among the gases.

It is almost insoluble in water.

It is a constituent of many gaseous fuels.

It is the lightest element.

Liquid hydrogen is used as a rocket fuel in space programme.

Through hydrogenation of coal, petrol is produced.

Also, used in the production of Vanaspati-ghee', through hydrogenation of vegetable oil.

Fuel of the future: Hydrogen.

Hydrogen is used in the extraction of certain rare metals.
eg: tungsten (used as electric filaments) and molybdenum (used in radio waves).

Carbon

Carbon is the first element of group 14 of periodic table.

It has maximum tendency of catenation (self linking property) in comparison to any other element in the periodic table.

It ranks 17th in order of abundance in earth crust.

Naturally occurring carbon contains two stable isotopes. 12C and 13C along with traces of 14C.

The crystalline allotropes of carbon are diamond, graphite, fullerene, graphene.

Amorphous allotropes of carbon are coal, char-coal and lamp black.

Diamond

The atoms of carbon are joined in a three dimensional tetrahedral structure in diamond.

Diamond is brittle, crystalline and the hardest naturally occurring substance.

It is the densest form of carbon.

Transparent to light and X-rays, it is a good conductor of heat, but not of electricity.

It is insoluble in all known solvents.

It is used for cutting glass.

Graphite

Graphite has a layer structure.

It has slippery nature and it is used as lubricant.

Graphite shows electrical conductivity due to the presence of π - electrons.

Graphite is used for making electrodes.

It is used in lead pencils in the form of mixtures with clay.

Graphite is known as 'black lead'.

Graphite is a good conductor of heat and electricity.

Fullerene

Fullerenes take the shape similar to that of ball.

Two important members of fullerenes are C60 and C70. C60 has been named as Bucktminster fullerene.

Graphene

Graphene is the newly discovered allotrope of carbon.

It consists of a single layer of carbon atoms arranged in hexagons.

Carbon features

Atomic number - 6

Maximum tendency of catenation

Allotropes - Crystalline & Amorphous

Crystalline -> Diamond, Graphite, Fullerence, Graphene

Diamond -> Hardest Known naturally as occurring black substance -> Densest form of carbon -> Three dimensional tetrahedral structure

Graphite -> Known as black lead -> Used for making electrodes, lead pencils etc -> Layer structure -> Used as lubricant

Amorphous -> Coal, Charcoal, Lamp black

Nitrogen

The element nitrogen was discovered by Scottish physician Daniel Rutherford in 1772.

In the free state, nitrogen constitutes nearly 80% of the air.

Nitrogen is the largest single constituent of the Earth's atmosphere (78.082% by volume of dry air, 75.3% by weight in dry air).

Atomic number — 7

Nitrogen obtained from air through fractional distillation is called Atmospheric nitrogen.

Nitrogen obtained from nitrogenous com-pounds is called Chemical nitrogen.

Nitrogen is neither combustible nor a supporter of combustion.

Nitrogen is a non-poisonous gas. Nevertheless animals die in an atmosphere of nitrogen for want of oxygen they need to breathe.

The Nitrogen Cycle: The sum total of the transformations undergone by nitrogen and nitrogenous compounds in nature in relation to the living organisms.

It is created by fusion processes in stars, and is estimated to be the 7th most abundant chemical element by mass in the universe.

Oxygen

Oxygen was first prepared by Karl Scheele. The credit of its discovery goes to Priestley (1774). Its elemental nature was established by Lavoisier.

Oxygen is a colourless, tasteless and odourless gas.

Liquid oxygen has light blue colour.

Oxygen does not burn but helps things to burn.

Atomic number is 8.

Oxygen was paramagnetic in nature.

The most abundant element on the earth crust.

The first synthetic atom is oxygen – 17.

It is the most abundant element present in our body.

It is a member of the chalcogen group on the periodic table.

Oxygen is the third most abundant element in the universe by mass after hydrogen and helium.

All major classes of structural molecules in living organisms, such as proteins, carbohydrates and fats, contain oxygen.

Smelting of iron ore into steel consumes 55% of commercially produced oxygen.

Sodium

It is found in the form of sodium chloride, sodium nitrate (Chile salt peter), sodium sulphate (Glauber's salt) and borax (sodium tetraborate)

Sodium carbonate (Washing soda) and sodium bicarbonate (Baking soda) are the main compounds.
 
Sodium is extracted through Down process.

It is stored in kerosene. a Liquid sodium is used as a coolant in atomic reactors.

The metal which regulates blood pressure in human beings is sodium.

Aluminium

Aluminium is the most abundant metal on the earth's crust.

The typical ores of aluminium are bauxite, corundum and cryolite. Aluminium is most widely extracted from bauxite.

Aluminium is one of the lightest metals, weighing only 2720 kg per cubic metre. This is about one-third of the weight of steel.

Aluminium is a good conductor of electricity.

Commercially, aluminium is extracted from Bauxite through a combination of the Baeyer's process and the Heroult - Hall process.

CD is produced by Aluminium.

Aluminium is an amphoteric metal.

Sulphur

It is a member of chalcogen family.

In the free state, sulphur is found in volcanic rocks and gases.

In combined state, it occurs as, metal sulphates: Gypsum, Glauber's salt, Epsom salt, Barytes. Metal sulphides: Iron pyrites, Copper pyrites, Galena, Zinc blende, Cinnabar (ore of mercury).

Coal and crude petroleum contain traces of sulphur.

Organic compounds present in egg protein, onion, garlic and wool also contain small quantities of sulphur, which gives them a unique odour.

Sulphur is non-poisonous to humans but toxic to lower organisms.

Its commercial uses are primarily in fertilizers, but it is also widely used in black gunpowder, matches, insecticides and fungicides.

Sulphur is used in ayurvedic medicines. In allopathy, sulphur based ointments are used for the treatment of skin disorders. Sulpha drugs are used as antibiotics to fight bacteria and colloidal sulphur is used in medicines for blood purification.

The enemy of copper is Sulphur.

Gold

Gold is considered to be the king of metals.

Symbol - Au

Atomic number - 79

Most ductile metal.

Purity of gold is expressed in carat.

Purest gold is 24 carats (99.94% Au).

Gold used for making jewellery is 22 carats. (916 gold).

18 carat gold - Gold (75%) + Copper (25%).

12 carat gold - Gold (50%) + Copper (50%).

Gold is soluble in aquaregia and in mercury.

Generally small quantity of other metals like copper arc added to gold to make it hard.

Why are noble gases called rare or inert gases ?

Ans: Noble gases are called 'rare gases', as they are present in very small quantities in the air and as as they do not enter into chemical reactions they are called `inert gases'.

Gold (Au) Features

Atomic number - 79

King of metals

Most ductile metal (drawn into wires)

Soluble in aqua regia, mercury

Carat (Purity) -> 24 carat (Purest gold - 99.95% Au), 22 carat (Jewellery making, 916 [91.6% Au + 8.4% Cu]), 18 carat (75% Au + 25% Cu[3:1]), 12 carat (50% Au + 50% Cu [1:1])

Iron and Steel

Haematite and magnetite are the richest ores of iron, containing upto 70% iron.

Limonite has 60% iron, pyrite and siderite contain 50% iron while taconite contains 30% iron.

The three commercial varieties of iron are cast iron, wrought iron and steel.

Cast iron (Pig-iron) is the impure norm of iron, contains highest proportion of carbon (2.5 - 4%)

Wrought Iron (Malleable iron) is the purest form of iron, contains minimum amount of carbon (0.12 - 0.25%)

Steel is the most important form of iron, contains 0.2 - 1.5% carbon.

Steel containing 0.2-0.5% carbon is known as mild steel.

Steel containing 0.5-1.5% carbon is known as hard steel.

Stainless Steel contains iron, chromium, nickel and carbon.

Nickel steel contains Iron, nickel and carbon.

Tungsten steel contains iron, tungsten and carbon.

Chrome vanadium steel contains iron, chromium, vanadium and carbon.

Zinc

At ordinary temperature zinc metal is brittle but on heating at 120-150°C it is malleable and ductile.

The most important ore of zinc is zinc blende.

Calamine and zincite are other important ores of zinc.

Impure zinc is known as speller.

Zinc is used in galvanization and in dry cells.

Zinc is used in dye-casting because of its low melting point and high tensile strength.

Zinc, as a reducing agent, is used in the manufacture of perfumes and synthetic drugs.

The metal present on insulin is Zinc.

Chlorine

Chlorine is a member of halogen group.

It is a poisonous gas.

Chlorine, either as liquid chlorine or chlorine water, is used for bleaching.

Chlorine is used for sterilizing drinking water.

Bleaching powder is used as a bleaching agent.

Sodium hypochlorite is used as an antiseptic.

Chloroform is used as an anaesthetic.

Carbon tetrachloride is used as a solvent.

Poly vinyl chloride is an important plastic.

Chlorine is used as an oxidising agent.

Noble Gases

Noble Gases are Helium, Neon, Argon Krypton, Xenon and Radon.

Radon is not present in air.

Atomic number of Helium is 2.

Liquid helium is used as cryogenic.

Helium and argon are used for welding.

To prevent oxidation of metals such as magnesium and steel helium is used.

Helium due to its non - inflammability and less diffusion is preferred for filling weather balloons and airships.

Helium being less soluble in blood than nitrogen, it is mixed with oxygen and used for respiration by deep sea divers.

Helium was first discovered in Sun's atmosphere.

Neon is used in making advertising signs.

The inert gas, which produces crimson glow when an electric discharge passes through it is neon.

Argon is used to create an inert atmosphere in chemical reactions and in electric bulbs.

Krypton and Xenon are used in electrical valves and TV tubes and also in light houses and miner's lamp.

Krypton or hidden gas was discovered by W. Ramsay in air.

Xenon or stranger gas was discovered by W. Ramsay in air.

Radon is obtained from radioactive disintegration of radium.

The thermal conductivity of liquid helium is very high.

Helium is used to inflat air craft tyres.

Hydrogen -> Henry Cavandish -> Atomic no. 1 -> Most abundant element in the universe -> Explosive gas

Nitrogen -> Daniel Rutherford -> Atomic no. 7 -> Most abundant element in the atmosphere -> Neither combustible nor a supporter of combustion

Oxygen -> Priestley -> Atomic no. 8 -> Most abundant element on the earth's crust -> Helps things to burn

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