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Manhattan project

The Manhattan Project was the development of the atom bomb. The first atomic bomb was developed at Los Alamos in the United States by an international team of scientists and exploded in the Alamogordo desert in New Mexico on 16 th July 1945. A leading statesman at the time quoted from the book of Hosea "They have sowed the wind, they shall reap the whirlwind".

Fortunately for our world only two atomic bombs have ever been dropped in war, on the cities of Hiroshima and Nagasaki in Japan. Recently it has been revealed that during the Cuban missile crisis of 1963 the Cubans were ready to use tactical nuclear weapons against the United States troops should they have launched an attack on the Cuba. It is thought that this would have plunged the world into nuclear war.

Statistics often mean little and sources do not always agree but it seems likely that about 100000 people died at 8.10 am on 6th August 1945 when the first atomic bomb was dropped on Hiroshima, and many thousands more died later as a result of the burns and radiation that they received. Three days later a second bomb was dropped on Nagasaki - 70 000 people died.

The bomb dropped on Hiroshima was 0.71m in diameter, 3m long and had a mass of 4000 kg and a destructive power of 20 000 tons of high explosive. It was exploded 300 m above the ground for "maximum effect".

Clearly the Cold War and the problems in Iraq, North Korea, India and Pakistan have shown the dangers of the spread of nuclear weapons. The cities of Hiroshima and Nagasaki were each destroyed by just one bomb and the nuclear stockpile of the early 1990s was some 50 000 warheads, equivalent to 1.5 million Hiroshima bombs. This represented the equivalent of about four tons of high explosive for every man, woman and child on the planet. Fortunately since then many of these weapons have been destroyed but it will only need one to start a catastrophe.

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Anyway to go on to isotopes.

Almost all elements have naturally occurring isotopes and many more can be made in the laboratory.

Isotopes of an element have the same number of protons but a different number of neutrons.

Basically, isotopes of an element are all the same element (they have the same number of protons) but they have different masses.

Carbon 14 (6 protons and 8 neutrons) and carbon 12 (6 protons and 6 neutrons) are two isotopes of carbon.

The chemical properties of all the isotopes of an element will be the same but their physical properties will be different because of their different masses. This means that properties like the boiling point and density of isotopes of an element will be different. For example 'heavy water' containing the isotope of hydrogen with a proton and a neutron in the nucleus (called deuterium) has a boiling point of 104oC.

Radioactive isotopes (radio isotopes) are ones that are radioactive and emit either alpha, beta or gamma radiation. These are used for a variety of purposes in medicine and industry.

In the fallout cloud after a nuclear explosion there are many radio isotopes and these fall onto the land below as a radioactive dust. The half lives of these radio isotopes may be quite long (often many years) and so the land will be contaminated far into the future. Caesium 137 is one possible result it has a half life of 28 years. The so called "dirty bomb" is a bomb surrounded by a material that can be made radioactive such as cobalt in the explosion cobalt 60 is produced with a half life of 30 years and this falls as a radioactive cloud over the population below. An unpleasant prospect.

© Keith Gibbs 2011