Scientific journalism is gradually catching up in Third World countries. This is welcome news and a healthy development.
Science, being the basic proven tool that can be harnessed to eradicate poverty, deserves greater attention. Journalists, among whose responsibility is the effective dissemination of information to the public, and other members of the public deserve every right to know what the atom is all about. I have chosen the atom for a down-to-earth discussion, since it is the building block of all matter and the foundation stone upon which science itself is built.
Without matter there will be no science, and without the atom there will be no matter. This is necessitated by the fact that scientific language in most part is too subtle and technical.
The idea of the atom was introduced by Greek philosophers as far back as 400BC, which is separated from our era by as much as 2,400 years. They reasoned that if you take up any matter, say a piece of sulphur, iron, gold, copper, silver or mercury and you continuously break it into pieces, a point would be reached when the last bit of the broken up matter cannot be subjected to further breaking. In other words the piece of broken matter has reached the ultimate in terms of small size.
That infinitesimally or vanishingly small size they named ‘atomos’, (the atom) which in the Greek language means ‘that which is uncuttable’. From this explanation, you can appreciate the fact that the atom is not perceivable, neither is it something you can feel palpably.
On this basis they propounded another hypothesis, namely that the atom is the building block of all matter and the entire universe. At the time of its birth the atom was a mere philosophy not subjected to the acid-test criterion of experiment. Yet the Greek philosophers were convinced beyond the least shadow of doubt about the reality of what they hypothesized.
To cut a long story short, scientists at the beginning of the 19th century began to subject the atom to experimental method. The first of such crucial experiments was that conducted by Dalton at Cavendish in 1803. He reacted pairs of chemical elements to form substances (molecules) and then analyzed the composition of the latter. He discovered that the elements always combined in simple ratios or proportions.
For example, two parts of hydrogen (H) will always combine with one part of oxygen (O) to produce water (H2O). This he correctly interpreted to mean that two atoms of hydrogen combined with one atom of oxygen produce water. Thus the reality of the atom being responsible for chemical reactions that resulted in the formation of substances or molecules was confirmed.
So far so good, for the discovery of the atom as an entity. As to what constitutes the atom, little was known about it. In 1898, J.J Thompson began an experiment with the conduction of electricity through gases and discovered the electron as a basic component of the atom. The electron is negatively charged hence written as e-.
In the same vein, scientists also discovered another fundamental particle of the atom which they called the proton. It is positively charged, hence written as H+. If the electron is negatively charged and the proton is positively charged then in combination the atom becomes electrically neutral (e + H+ —>H).
Series of experiments were subsequently conducted to discover more about the atom. One such experiment was conducted by Rutherford in 1909 using alpha particles to bombard a thin foil of gold. Through this experiment he discovered that the atom had a central part which he named as the nucleus. He also discovered that all the positive particles, called the proton (H+) and the entire weight of the atom were concentrated in the nucleus.
Later a particle having zero charge (chargeless) was discovered by Chadwick in 1932. He named it as a neutron and is also housed in the nucleus alongside the protons. It served to interpose amongst the positively charged protons in order to prevent them from repelling each other, which could destabilise the atom.
The situation is just like peacekeepers interposed amongst combatants to keep them from fighting each other. Not only did scientists discover this or that particle but also carried out measurements to determine the sizes of the nucleus and the masses of the constituent particles. Here are the corresponding data:
The radius of the nucleus: 1.4x 10-15 m; the mass of the electron: 9.1083x 10-31 kg; the mass of the neutron: 1.67470x 10-27 kg; the mass of the proton: 1.67239x 10-27 kg; density of the nucleus: 1.45x 1017 kg/m3. You will, here, appreciate the fact that the dimensions of masses of the atom are such that they can never be measured by the most sensitive veneer caliper, or by the most sensitive electronic balance.
The data are obtained from measurements coupled with the power of mathematical calculations. Notwithstanding this, you will simultaneously appreciate the fact that the density of the nucleus of the atom is the highest in the entire universe. As pointed out in previous articles, this equals the density of matter in the core of the sun when the latter collapses.
In effect there are a lot of similarities between the core of the sun and the nucleus of the atom. In 1913, Bohr clearly brought out the similarities by proposing that electrons are arranged around the nucleus of an atom in the same way as the planets are arranged around the sun. The planets revolve around the sun in concentric circles just as the electrons revolve around the nucleus in concentric circles. This theory he called the planetary model of the atom.
Let us at this stage therefore try to visualise the atom as a miniaturised solar system in which the negative electrons revolve around the nucleus in circles, just as the planets including our earth revolve around the sun in circles. You will recall from your knowledge of geography that the names of the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
Each spins on its axis as well as revolves around the sun at the same time. The planet closest to the sun, Mercury, is too hot for life to exist there. Similarly electrons are arranged around the nucleus in orbits with each electron or group of electrons in an orbit spinning on their axis and revolving around the nucleus at the same time. In effect the nucleus of the atom is analogous to the sun, whilst the electrons are analogous to the planets.
Like Mercury, which is too hot and hostile to the evolution of life, the electrons found in orbits closest to the nucleus are more energetic than subsequent layer of electrons found in other orbits. Let us end our first lesson here and try to master the concepts that we have learnt so far. Kindly consult the figures below as you read along.
In conclusion, the atom is a miniature solar system. The nucleus contains the positive protons and the neutral neutrons, whilst the negative electrons spin on their axis and revolve around the nucleus simultaneously.