Why should we learn about Atomic Structure?

Now this is an interesting question. Since millennia, man has been trying to unravel the mysteries of this universe. With science and technology carving out new frontiers on a regular basis, one must wonder what was it that allowed humankind to keep seeking and exploring more frontiers for knowledge. A lot of the credit for us to have reached this state should go to the discovery of the atom and its constituents. Science has never been the same again since its discovery, and the role of atoms as the building block of anything has already been proven.

No matter how big or how small, the building block of any matter is atom. Atoms are the basic creating blocks of everything in the cosmos, whether it be natural or be it manmade. These atoms are so small that one will discover millions of atoms in a single dot of dust. Electric current, occasionally known as electricity, is the flow of tiny constituent of this atom called electrons. Can one imagine a life without electricity? For anything that we see, touch, create, invent or discover, nothing would be possible without the atoms.

Let us discuss what atomic structure is. Atomic structure discusses to the configuration of an atom. The atom comprises of a nucleus, which is the center of the atom. The nucleus houses the neutral neutrons and the positively charged protons. The negatively charged particles of the atom are called electrons and these electrons revolve around the nucleus in fixed orbits, depending on the atomic number of the element that constitutes the matter. The electrons are held in their place inside the orbits due to the attractive force of the nucleus.

The account of atomic structure and quantum mechanics goes back to the days of Democritus. Democritus proposed the idea that matter must be composed of something tiny, and thus, matter must be composed of atoms. The study of the structure of an atom provides a great understanding into the complete class of chemical reactions, bonds and their physical and chemical properties. In the 1800s, John Dalton proposed the first scientific theory for the structure of the atoms. He proposed that all the matter in the universe was made up of atoms, and these atoms were indestructible and could be further divided. He also stated that all the atoms of element were similar; however, different elements had different atomic size and mass. He also stated that chemical reactions were in fact mechanism for rearrangement of atoms to yield new products. However, his theory failed to explain the occurrence of isotopes and since he believed the atoms were indivisible, no clear idea about atomic structure was available.

Since it was discovered that atoms were indeed divisible, it led to the acceptance of existence of subatomic particles. With the discovery of subatomic particles, it became easier to explain and understand the chemical species. From here, more atomic models came into being.

In early 1900s, Sir Joseph Thomson, an English Chemist, proposed his theory of atomic structures. His work was so ground breaking that Nobel Prize was bestowed upon him for his contribution for discovering the electrons as a subatomic particle. He proved the existence of the electrons by the famous cathode ray experiment. However, Thomson’s theory was unable to explain why the atoms were stable and also, it left no scope for other subatomic particles to be placed in his model.

After Thomson, came the atomic theory proposed by his student called Rutherford. He was able to modify the Thomson’s model with the finding of another subatomic particle called the "Nucleus". It was his experimentation on Alpha ray scattering that led to this discovery. Rutherford proposed that based on his findings, there was a nucleus located at the center of the atom, that houses most of the charge and mass. He also proposed that the structure of the atom was spherical and that electrons revolved around the nucleus like the planets that revolve around the Sun. However, his model was unable to explain what held the electrons to orbital path. This was clearly so because till then the protons were not discovered.

Now we all know that the atomic structure consists of subatomic particles called neutrons, protons and electrons, and the electrons revolve around the nucleus. Let us see some important properties of these subatomic particles.

Check One Example

Question: Which one of the following substances is NOT a mixture?

Answer: https://www.doubtnut.com/question-answer-chemistry/which-one-of-the-following-substances-is-not-a-mixture--52787316

Proton:

• They are the positively charged subatomic particles having a charge of +1e.
• It has a mass of about 1.672 × 10-24 and thus are around 1800 times heavier than the electrons.
• The atomic number of the element decides the number of protons in the nucleus.

Neutron:

• Neutrons are electrically neutral and have no charge.
• It has the same mass as that of the proton.

Electrons:

• The electrons are negatively charged subatomic particles with a charge of -1e and mass of around 9.1 X 10-31
• Due to the comparatively tiny mass of electrons, they are not considered during the computation of the mass of the atom.

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