The facts about the atom’s discovery are not easy to explain. John Dalton (late 1700s) was the first to perform experiments that determined atomic weight. But the ancients had already postulated its existence, though they weren’t able to prove it.
The Idea of the Atom
The concept of matter being made up smaller particles that couldn’t be divided goes back to ancient India in 6th century BCE. The idea of atoms was also recognized by the Greeks. In 450 BC, Democritius wrote that all matter was composed of particles that could not be cut.
However, these theories were based on philosophy. The facts about the atom would not emerge until the 1600s when scientific instruments began to be invented.
It began with Robert Boyle in 1661. He stated that matter was comprised of small particles and not the four elements. Antoine Lavoisier was the one who proposed that the atom could not be divided by methods used in chemistry. It was Dalton however, who relied on experiments to prove their existence.
In 1827, Robert Brown used a microscope to observe the motion of dust in water. His theory was that it was caused by molecules and small particles. This was followed in 1905 by Albert Einstein’s theory on motions.
In 1909, Ernest Rutherford blasted a gold foil sheet with alpha rays. It was this experiment that led Rutherford to conclude that the atom’s mass was centered in the nucleus. This fact about the atom would have a tremendous impact on atomic theory and development. Subsequent research has shown that the atom is composed of smaller particles.
The Subatomic Particles
The atom is made up of several subatomic particles. These include the electron, neutron and the proton. The electron is the smallest of these particles and has a negative charge. It is so small it
cannot be measured yet.
The proton has a positive charge and is 1,836 times bigger than the electron. Neutrons do not have a charge. They are 1,839 times larger than the electron. In terms of size, neutrons and protons are about the same.
As more facts about the atom surfaced, it became clear protons and neutrons were made up of even smaller particles called quarks. Quarks and leptons are regarded as some of the most basic elements of matter. There are half a dozen quarks known today, each with a charge.
Protons are comprised of three quarks (2 up and 1 down). The neutron is made up of 1 up quark and 2 down quarks. The quarks are held by the nuclear force and the gluons. The gluons are among the most basic particles that intercede physical forces.
The protons and neutrons are in the nucleus, which is a small part of the atom. These particles are jointly known as nucleons. The nucleons are held together by the residual strong force.
More facts about the atom are emerging as scientific instruments improve. While much has been learned, there are still facets of this particle that are waiting to be discovered.