What is an Atom

Atom is the smallest unit of ordinary matter that forms a chemical element. Every solid, liquid, gas, and plasma is made up of atoms. They are composed of neutral atoms. We are surrounded by atoms as everything comprises of it. From neutrons to electrons and from electrons to their mass and its nucleus.


electron mass nucleus neutron

In layman’s term for atoms

If you eat something that thing is made up of atom. You, me, and everything you see is made up of atom.

History of atoms

The basic idea that matter (things you can touch, feel, and see) is made up of tiny indivisible particles is very old. It appears in many ancient cultures like Greece and India. As this idea is based on the philosophical ground, the modern atomic theory is not like that.

In the early 1800s, an English chemist (John Dalton) compiled experimental data gathered by himself and other scientists and they discovered a pattern. Later named as ‘Law of multiple proportions’.

He noticed that in chemical compounds that contain a particular element. The content of that element in these compounds will differ by ratios of small whole numbers. By looking at this pattern Dalton understood that each chemical element combines with others by some basic and consistent unit of mass.

Brownian motion

The brownian motion experiment

In the year 1827, Robert Brown was a botanist by profession. He looked at dust grains that were floating in the water and noticed a similarity. That they moved erratically. This phenomenon later called ‘Brownian motion’.

In 1905, Albert Einstein proved the reality of these molecules and the motion by producing the very first statistical physics analysis of ‘Brownian motion’.

Later on French physicist ‘Jean Perrin’ used Einstein’s work to experimentally determined the dimensions and mass of molecules and providing physical evidence of particles and the nature of matter.

What is electron

Electron is a subatomic particle that is found inside atoms, they were discovered by J.J.thompson in the year 1897 when he noticed that there is a particle that is 1,800 times lighter than ‘Hydrogen'(it is the lightest gas). It was easily recognized that electron particles contain electric currents in metal wires. That’s when the electron was discovered and the name electron was given because of its charge.

Discovery of nucleus

Illustration of Nucleus

Between 1908 and 1913, Rutherford and his colleagues performed some experiments in which they bombarded thin foils of metal with alpha particles (these particles have a positive charge which is emitted by certain radioactive substances such as radium) They spotted alpha particles being deflected by greater angles than 90 degrees. After this experiment, Rutherford proposed that the positive charge of the atom is not distributed throughout the volume of the atom as Thomson believed, but is concentrated on a tine nucleus at a center.

Discovery of isotopes

When Frederick soddy who was a radiochemist by profession was experimenting with the products of radioactive decay, in the year 1913 he observed that there is more than one type of atom at each position on the periodic table. The term isotope was coined by Margaret Rodd as a suitable name for different atoms that belong to the same element.

Discovery of neutron

Illustration of neutron

Neutron, is an uncharged particle with a mass similar to the proton, by the physicist James Chadwick in 1932. Isotopes then explained as elements with the same number of protons, but different numbers of neutrons within the nucleus. It was discovered when chemist Francis William Aston used the instrument mass spectrometer (an instrument which allows the mass of atoms to be measured with increased accuracy) to show that isotopes have different masses the atomic mass of these isotopes varied by integer amounts, also known as the whole number rule. The explanation of these different isotopes awaited the discovery of the neutron, an uncharged particle with the same mass as the proton. Isotopes were then explained as elements with the same number of protons, but different numbers of neutrons within the nucleus.

What is a Nucleus

All the bound of protons and neutrons in an atom make up a tiny atomic nucleus which is collectively called nucleons. Atoms of the same element and with the same number of protons called the atomic number within a single element, the number of neutrons may vary, determining the isotope of that element. the total number of protons and neutrons determines the nuclide. the stability of the nucleus is determined by the number of neutrons relative to protons, with certain isotopes going under radioactive decay.

What is mass

The word mass has been come up a number of times in the blog but what does it truly mean. The large majority of an atom’s mass comes from the protons and neutrons that make it up. The total number of these particles in a given atom is called the mass number. It is a positive integer and it is dimensionless (instead of having a dimension of mass) because it expresses a count. The mass of an atom at rest is expressed as daltons(Da) also known as a unified atomic mass unit (u). As even the massive atoms are far too light to work with directly. That’s why chemists instead use the unit of moles.

To conclude

There is a lot more to scratch in the study of a universe from the black holes to the quarks. From the Orian Nebula to sub-atomic particles. Atom is just one part of that whole big world.


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