Category Chemistry

               Quantum mechanics helps us to understand how energy is used or released by atoms. Negatively charged electrons circle about the positively charged nucleus of the atom. They stay in the same orbit, until this is disturbed, and each orbit has its own level of energy. If more energy is added, when the atom is heated or when light shines on it, the electron jumps out to another orbit, absorbing the extra energy. Then when it drops back again to its original orbit, it releases this energy as heat or light. This tiny packet of energy is called a quantum. Heisenberg’s Uncertainty Principle states that it is not possible to measure exactly where a subatomic particle is and how fast it is moving, because any attempt to measure it will disturb the particle and change its characteristics.

               Atoms consist almost entirely of empty space, because almost all their mass is concentrated into the nucleus. If an atom were enlarged to the size of a football, its nucleus would still be too small for you to see it with the naked eye.

What are electrons?

               Electrons are the very tiny particles that travel around the nucleus of an atom at incredibly high speed. They carry a negative electrical charge.

               The circling electrons are arranged in different layers called shells. If there are many electrons circling around the atom and the outer shell is full, the atom will not react with other substances. If the outer shell is not full, the atom can gain or lose its electrons as it reacts chemically with other atoms around it.

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               The centre of an atom is its nucleus, which has shells of electrons hurtling around it. The nucleus consists of protons, which are electrically charged particles, and neutrons, which have no electrical charge at all. The nuclei of similar atoms usually contain the same numbers of electrons and protons, but sometimes the number of neutrons varies. These atoms with different numbers of neutrons are known as isotopes.

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               There are many smaller particles, and more are being discovered. These very small particles are known as subatomic particles. The electron revolving around the atom, and the neutron and the proton that make up the nucleus, are all subatomic particles.

               Another type of subatomic particle is the positron. It is the same as an electron but with a positive electrical charge. If a positron collides with an electron they are both destroyed and form a shower of even smaller particles. Even neutrons and protons are thought to consist of even smaller particles, called quarks. Photons, gluons and bosons are other forms of subatomic particles, and there may be as many as 100 different types altogether.

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               Atoms are the smallest pieces of matter. They are the tiniest particles into which a substance can be divided without changing into something else. Atoms actually consist almost entirely of open space, in which tiny particles orbit the central particle, or nucleus. The particles travel so fast that they seem to be solid.

               Atoms are so tiny that the smallest particle visible to the naked eye would contain about one million billion atoms. Despite their tiny size, atoms can be seen individually under very powerful electron microscopes.

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