2. Historical Background on the
Development of the Atomic
Theory
The Greeks were the first to propose physical explanations for materials. And the idea
that matter is made up of ultimate particles was advanced as early as the fifth century
B.C by the ancient Greeks.
Thales developed a Babylonian idea that the world was created from the waters. He was
interested in astronomical, physical, and meteorological phenomena, and his scientific
investigations led him to speculate that all natural phenomena are different forms of one
fundamental substance. He believed this substance to be water, because he thought
evaporation and condensation to be universal. To him, every substance is nothing but
water, but appearing in different forms. Water exhibits all the known states of
matter, solid, liquid, and gas, and is clearly essential to life as well. Before
Thales, explanations of the universe were mythological, and his thoughts on the basic
physical substance of the world mark the birth of the scientific thought
3. Anaximandros agreed with Thales that the world is made of some basic elements. But
Anaximandros refuted Thales’ claims about matter. Instead, he thought that element was
some undetermined material he called apeiron, “the boundless”. He postulated that this
substance is eternal and indestructible. The various objects and organisms that make up the
recognizable world are a result of the ceaseless motion of apeiron. And that the more familiar
‘substances’ in his time such as warmth, cold, earth, air, and fire continuously evolve to form
the world.
Anaximenes the last member of the Ionian school founded by the philosopher
Thales, claimed that air (pneuma), not water, is the element material. The presence of so
many kinds of substances is allegedly due to thickening or thinning of air. To explain how solid
objects are formed from air, he introduced the concepts of condensation and rarefaction.
According to him, these processes transform air, in itself invisible, into something visible—as
water, fire, and solid matter. He thought that air becomes warmer and turns to fire when it is
rarefied and that it becomes colder and turns solid when it is condensed
Heraclitus suggested everything consists of fire or some other single material and that is
changed by eternal flux (then meaning up and down motion). He postulated that through
condensation and rarefaction, fire creates the phenomena of the sensible world.
Anaxagoras suggested that the world is essentially complex and divisible seeds controlled by
mind. The component seeds of everything are the same nature as the thing itself. He held
that all matter had existed originally as atoms, or molecules; that these atoms, infinitely
numerous and infinitesimally small, had existed from all eternity; and that order was first
produced out of this infinite chaos of minute atoms through the influence and operation of
an eternal intelligence. He also believed that all bodies are simply aggregations of atoms; for
example, that a bar of gold, iron, or copper is composed of inconceivably minute particles
4. of the same material.
Empedocles thought there were four original elements: Earth, Air, Fire, Water. He thought
everything else came about through their combination and/or separation by the two opposite
principles of attraction (love) and repulsion (strife). The first “atomic theorists” were two 5th
century B.C Greeks, Leucippus of Miletus (a town now in Turkey) and Democritus of Abdera.
Leucippus’ theory was a reaction to the theories of Parmenides and his pupil, Zeno, who
believed that the formative substance of the universe was the one, an infinite, all
encompassing, motionless mass that contained no empty space. Leucippus theorized that this
was not correct because our senses tell us that there is motion. He argued that void, the
absence of anything that exists, is necessary for motion. He also postulated that an infinite
number of particles or atoms form what exists and that the dissolution of these particles leads
to the destruction or death. Their theories were naturally more philosophical than
experimental in origin because they were not experimental people. Of course, this was all pure
conjecture, but the physical pictures the described sometimes seem uncannily accurate.
Democritus believed that matter consisted of tiny particles called atomos and that the infinite
variety of observable things could be explained by the combinations of different sizes and
shape of these particles. Basically, Democritus and his followers had a very mechanical picture
of the universe. They thought all natural phenomena in principle could be understood in terms
of interacting, usually moving, atoms.
Plato proposed a mathematical construction of the elements- earth, air, fire, water . Each of
these elements is said to consist of particles or primary bodies. According to Plato, each
particle is a regular geometrical solid – the cube, tetrahedron, octahedron, and icosahedron.
Each of these particles is composed of simple right triangles.
5. The particles are likened to the molecules while the triangles are the atoms of the molecules.
Little conceptual progress in atomic theory was made over the next two thousand years, in
large part because Aristotle discredited it, and his views held sway through the Middle Ages.
Aristotle rejected the idea of the atomism of matter. He believed that there is no limit to
subdividing matter. Dividing matter in small bits can go on infinitely with each piece getting
smaller and smaller.
Epicurus was atomistic, in the tradition of the Greek philosophers Leucippus and Democritus.
Epicurus regarded the universe as infinite and eternal and as consisting only of bodies and
space. Of the bodies, some are compound and some are atoms, or indivisible, stable elements
of which the compounds are formed. The world, as seen through the human eye, is produced
by the rapid circular movements, collisions, and aggregations of these atoms, which
individually possess only shape, size and weight. He taught that the soul is composed of fine
particles distributed throughout the body. He alleged that when the body dies, the soul
disintegrates and dies, too.
Titus Lucretius Carus wrote a long poem De Rerum Natura or On the Nature Things nominally
to a Roman statesman, Gaius Memmius, governor of the Roman province Bithynia in 57 B.C.
Much of what we know of the Greek view of atoms comes from that book-length poem.
Lucretius poem suggests that all knowledge is derived from the senses. According to his
poem, things are exactly as they appear to be our senses, or as they would appear if our
senses were more acute. Because material objects are perceived, therefore they exist. He
stressed that nothing is ever created out of nothing is ever exterminated or destroyed. They
transform. Matter has invisible particles which are indestructible. Besides matter, the universe
has vacuum and nothing else.
6. Galileo Galilei Italian physicist and astronomer, believed in atoms, although, like the early
Greeks, he seemed to confuse the idea of physical indivisibility with that of having zero spatial
extent, i.e. being a mathematical point. Nevertheless, his ideas in this are apparently got him
into theological hot water. The Church felt that the doctrine of transubstantiation—the belief
that the bread and wine literally became the body and blood of Christ—was difficult to
believe if everything was made up of atoms. This was an echo of the tension between atoms
and religion two thousand years earlier. Galileo was also noted for his support of the
Copernican view that the Earth was stationary, and that attributing Earth to be moving
around the Sun was allegedly contrary to Scriptures. In his study about the tides, he wrote
Dialogue on the Tides but later on entitled by the Church as Dialogues on the Two Chief World
Systems to present the two contradicting views of the Earth’s movements in the universe.
Apparently, the ideas were Copernican-leaning. This led to Galileo’s infamous trial for “grave
suspicion of heresy”. He was compelled in 1633 to abjure and was sentenced to life
imprisonment. The Dialogue was prohibited and the sentence against him was to be read
publicly in every university.
In 1979, Pope John Paul II opened an investigation into the Galileo’s condemnation. This led
to the eventual acknowledgement of the error committed by the Church’s officials when they
sentenced Galileo for alleged heresy. Pope John Paul II acknowledged this in October 1992.
7. Robert Boyle he devoted himself to scientific research. Because he was a staunch believer in
the importance of objective observation and verifiable laboratory experiments in scientific
studies, Boyle is considered to be one of the founders of modern scientific method. He was
the first chemist to isolate an collect gas. Boyle’s law states that at constant
temperature, the volume of gas varies inversely with the pressure. In his book The Sceptical
Chymist, Boyle attacked the theory proposed by the Greek philosopher Aristotle.
Sir Isaac Newton mathematician and physicist and considered as one of the foremost
scientific intellectuals of all time. He postulated that the small particles of bodies act upon
one another by attractions of gravity, magnetism and electricity. He was explaining the
binding forces of atoms or the small particles he referred to. He thought that physical
matter could be explained in terms of the mechanics of corpuscles. He spent much time
figuring out how God ran the universe. He tried to provide an explanation on the ultimate
particles of matter and thought of them as the ultimate secret of how God designed the
material world.
Antoine Laurent Lavoisier he discovered that combustion was a chemical reaction between
the burning and a component of the air, disproving the phlogiston theory. One of his great
discoveries was that in chemical reactions, there is no change in the weight of the products
compared to the weight of the initial materials involved. He did a lot of experiments on
acid, he succeeded in producing more and better gunpowder by increasing the supply and
ensuring the purity of the components saltpeter (sodium nitrate), sulfur, and charcoal—as
well as by improving the methods of granulating the powder. He also made experiments on
the nature of combustion and respiration. He discovered that both are caused by the
chemical combination of a part of the air and that this same substance causes the formation
of acids.
