Atoms are the smallest unit of an element that can exist. The ideas of the atom started at 400B.C by the Greeks. In Greek philosophy, the word atom was used to describe the smallest bit of matter that can not be broken down. This name means that it is uncuttable or not divisible. The knowledge about the size and nature of the atom did not begin until the late 19th century.

John Dalton was a British chemist who developed an atomic theory that showed all matter is made up of particles called atoms and cannot be broken down any further. Although this theory was already been speculated, his theory can be measured. Dalton suggested that each element have varying properties because of the differences in the atom structure. Dalton then proposed that atoms of the same element are equal in size and weight. Today, we know that atoms can be broken down and that atoms of an element are not always identical. But Dalton became one of the important people in the atomic theory, and his ideas led the path to modern chemistry.

In 1897, a physician named Joseph John Thomson discovered that atoms could be broken down. This discovery was made when he was studying the rays that travelled between charged metal plates in a vacuum tube. Thomson determined that the rays consisted of light weighed, negatively charged particles in which he discovered electrons. He immediately thought that the electrons were embedded in a positively charged sphere (like seeds in a watermelon). The positive and negative charges would balance to make the atom neutral. Although Thomsons descriptions of the structure of the atom were inaccurate, his work encouraged other people to investigate deeper in to the atomic structure.

In 1911, a physician Ernest Rutherford proposed his theories of the atomic structure, stating that nearly all the mass of the atom is concentrated  into a tiny nucleus located at the centre/core of the atom. Surrounding it is negatively charged electrons travelling at high speeds and in different directions. Rutherford was the first to recognise the nature of the atom - they have a nucleus. His results were based on his experiments that he performed, where he surrounded a thin sheet of gold and passed a ray of alpha particles through it. As a result, most of the particles went through it because atoms mainly consisted of spaces. Some particles bounced off into another direction, as if it had hit something solid. This fact led to the idea of a nucleus inside the atom. Rutherford did not further explain the arrangements of electrons in the atom.

In 1913, a description of the electron structure was made by Niels Bohr. Bohr suggested that electrons could only travel in a certain orbit around the nucleus. He assumed that electrons were arranged in shell or levels, at a reasonable distance from the nucleus. The arrangements of the electron are called the electron configuration and can build up to a total of 7 shells; with each level have a limit of accommodation.
 

Only a few elements found on earth have radioactive isotopes. With the help of technology and new discoveries, over a thousand artificial radioisotopes can be made. Radioactive Isotopes can help our lives but sometimes can harm us. For example, in medicine, it is used to diagnose, give treatment and take images in our body systems. Inside our body, radiation may be used trace any abnormalities and also to kill cancer cells. When diagnosing, radioisotopes maybe injected to the body organs, where they are detected and are photographed to show the conditions of the body. There are some radioisotopes that can be used as batteries in heart pacemakers, where electric shocks will keep the heart beating. The advantage of this is that these pacemakers can run for over 20 years before replacing.

In industries and agriculture, working becomes much easier with the help of nuclear science. There are devices that can measure the thickness of paper, plastics and metals etc. and can detect underground leaks in pipes. Population of insects can be controlled and the help of radioisotopes accelerates the growth of plants.

The use in radioactive material can be hazardous if they are misused. Exposure to harmful radiation could be fatal, as living cells are destroyed. Sometimes the use in radioactive material has gone too far. For example, countries are now using them for mass destruction and wars. Lastly, radioactive waste that is produced must be found. The disadvantage is that we must find ways to keep them out of human exposure and that fact that it takes a long time for it to decay.

I believe that the knowledge of the atom and its implications has been a benefit to mankind. Without the knowledge of atoms and how chemistry works, I do not think life would ever survive on earth. The study of atoms had led to the world of of nuclear science, and from that, we have converted this knowledge into helping our lives. For example, raadioisotopes has prevented many errors in the human body. The use in nuclear power is a benefit, but on the other hand, the nagative side is that nuclear meltdown can harm us.

In the future, I believe that the use in nuclear science would be safer to use because as time goes by, we will begin to understand more and more about our world and how to control it. We would choose to do what is good for us and prevent things that may harm our lives.