ARTICLE

        Elements

                                     The elements are sometimes called the building blocks of the Universe because everything in the Universe-including ourselves – is made of them.The nucleus of each element consists of atoms with the same number of protons.Each element is unique,although elements can exist in different forms-for example,carbon may be soft but its another form diamond is the hardest among all substances.

                                   There are about 118 elements altogether,and 91 occur naturally on Earth.Others can be created artificially in laboratories,but in minute quantities and they have very short lifespans.

The heaviest &lightest elements

      Heaviest  elements

Osmium

Osmium is the heaviest element of all. It was discovered by the British chemist Smithson Tennant in 1803. He named it after the Greek word for smell because it smelt bad.  Osmium is twice as heavy as lead-so heavy that a cubic foot weighs 640 kg, as much as ten average people. It is used to make hard wearing points such as the nibs of fountain pens.

Platinum

 Platinum was used before any one realized that it was an element . It weighs almost as much as Osmium and is used to make jewellery that is even more expensive than gold.  It is also used in Catalytic converters in cars to reduce the pollution from exhaust gases.

Plutonium

Plutonium was discovered in 1941 and is heavy and highly radio active metal.  It is used as a nuclear fuel and nuclear weapons.

Gold

 Gold is the best known of all heavy metals – though at 19.29 g per cubic centimeter it is less heavy than the others here.

            lightest elements

Hydrogen

 Hydrogen is the simplest and lightest element,and the most common in the entire Universe-93 percent of all atoms in the Universe are hydrogen atoms. The air in a 

room with walls 4 m long and 4 m high would weigh 82.5 km but if the same room  were filled with hydrogen it would weigh only 5.76 kg. This is why it was used in balloons carrying human passengers.

Helium

 Helium is twice as heavy as hydrogen, but it is still only 1/7^th the weight of air.  Unlike hydrogen, helium does not burn, so it is used in modern airships.

Lithium

Lithium was discovered in 1817 by Swedish scientist Johan August Arfvedson.  It takes its name from the Latin word for rock, although it is actually a metal.  It is so light and so soft that it can be easily cut with a knife. It floats because it is half as heavy as water and lighter than some types of wood. It is used to make lithium batteries.

Potassium and Sodium

 Both were discovered in 1807 by Sir Humphry Davy. Both are metals that are lighter than water.  In Laboratory potassium is usually kept in paraffin because it comes into contact with water it releases hydrogen and generates so much heat that it catches fire. When sodium is dropped into water it hurtles around on the surface before noisley bursting into flames.  So it is also kept in Paraffin.