Written by Adeel Abbas
Evidence of atom has been searched for a long time in both the modern and classic chemistry period. Although the whole world is made of atoms no one has ever seen the atoms with the eyes. Since the advent of civilizations researchers are trying to collect evidence about the existence of atoms. Let us have a look at the earlier efforts put forward by the earlier scientists.
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Evidence of atoms by The Greek philosophers
Table of Contents
The views of earlier Greek philosophers about mater were not based on experimental evidences as they said that it could be divided into smaller and smaller particles that results in to basic unit which could not be further sub-divided.
These smallest indivisible particles were given the name ‘’atomos’’ by Democritus which means indivisible.
Evidence of atom in 17th Century work
In the late 17th century, the quantitative study of the composition of pure substances disclosed that a few elements were the components of many difficult substances. It was also investigated that how elements combined to form compounds and how compounds could be broken down into their constituent elements.
Evidence of atom by Dalton’s work
In 1808, John Dalton who by profession was an English school teacher recognized that law of conservation of mass and the law of definite proportions could only be explained by the existence of atoms. He also formulates a theory about atoms known as Dalton’s Atomic Theory. According to this atomic theory is that all matter is composed of atoms of different elements, which differ in their properties.
Definition of Atom
After consecutive efforts over a long period of time the definitions of atoms secured a place in literature books.
The smallest particle of an element that can take part in a chemical reaction is called an atom.
or
The smallest particle of an element which may or may not exist independently is called atom.
Examples
Atoms of He, Ne, Ar, Kr, Xe and Rn can exist independently while atoms of M, O, N etc. do not exist independently.
Sub-atomic particles
Modern research has revealed that an atom is composed of many sub-atomic particles like electrons, proton, neutron, hypron, boson, neutrino, antineutrino, etc.
Electron, proton, and Neutron are said to be important sub-atomic particles.
More than 100 such particles are thought to exist in an atom. However, electrons, protons, and neutrons are regarded as fundamental particles of atoms.
Berzelius’s work
Swedish Chemist J. Berzelius (1779 — 1848) has the following contribution to chemistry. He determined the atomic masses of elements. A number of his values are close to the modern values of atomic masses. He developed the system of giving elements a symbol.
Comparison of Berzelius’s Atomic Masses with Modern Values
| Element | Berzelius Value | Current Values |
| Chlorine | 35.41 | 35.45 |
| Copper | 63.00 | 63.55 |
| Nitrogen | 14.05 | 14.01 |
Berzelius contributed to chemistry by discovering Cesium, Thorium, Selenium, and Silicon.
Evidence of Atom
Although it is impossible to actually see the atoms because an ordinary optical microscope is able to measure the size of an object up to 500 nm. But direct evidence can be witnessed by an electron microscope.
Usually, the image of an object smaller than the wavelength of visible light cannot be taken.
Use of Electron Microscope
An object having its size equal to the atom can be measured by using an electron microscope because it uses beams of electrons instead of visible light. The logic behind this is pretty simple the wavelength of an electron is much shorter than that of the visible light.
Graphite image taken by the Electron Microscope
The following figure of a piece of graphite was obtained after magnifying about 15 million times. The brighter bands in the figure are layers of carbon atoms.
Evidence of atom by X-rays
During the 19th century, X-rays work showed that
Diameter of atoms are of the order 2 (10-10 m) or 0.2 nm or 2 Å
Masses of atomic range from 10-27 kg. These are expressed in atomic mass units( amu).
Conclusion
From the above-mentioned evidence, it is proved that atoms exist in much smaller sizes.
You can understand how smaller an atom is by the following example a Full stop may have two million atoms present in it.
FAQs about evidence of atom
How can you identify an atom?
Identifying an atom after the discovery of the latest electron microscope is no more an impossible factor. We can identify an atom using an electron microscope that uses a beam of electrons because the wavelength of electrons is shorter than the visible light.
Who is the father of Atom?
Although efforts to gather evidence about the existence of atoms had been continued by the earlier Greek Philosophers. However, they could not provide evidence of the atom on the experiment base. Therefore, John Dalton is considered to be the father of atoms. He presented His theory known as Dalton’s Atomic theory.
What is an atom and example?
An atom is the smallest unit of an element or compound. Example: Hydrogen.
How does an atom work?
An atom has a nucleus, and electrons orbiting it.
Why do we call atoms “atoms?”
The term was coined by English chemist Joseph Priestley in the early 1700s. He believed that the smallest parts of nature, and particular matter, were minuscule. Today, we know these particles are made up of more fundamental particles.
How many subatomic particles are there in a nuclear atom?
A single atomic nucleus contains approximately 1,800 subatomic particles, including protons, neutrons, and electrons.
Does an atom contain all the same elements?
All atoms are composed of the same set of chemical elements, but they vary in their relative amounts. For example, one atom of hydrogen (H) may have one electron, one proton, and a half-dozen neutrons. An atom of helium (He) may have one proton, one neutron, and one electron.
How do I identify different elements?
The atoms of an element have the same number of protons in the nucleus and the same number of electrons surrounding the nucleus.
What’s the difference between an isotope and an atom?
Atoms of the same element can have different numbers of neutrons. These are called isotopes.
How is an atom composed?
All atoms are made up of the same basic building blocks—protons, neutrons, and electrons. A simple atom consists of one nucleus with varying numbers of protons and neutrons. The mass of the atom (the sum of its protons, neutrons, and electrons) is its atomic mass.
What is the chemical symbol for an atom?
Chemical symbols are used to represent the various elements. Chemical symbols are composed of two parts: the first part, the “atomic symbol,” stands for the element and the second part, the number, tells you the number of protons in the nucleus.
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