Structure of Atom
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Several scientists tried to describe the structure of the atom through atomic models during the 18th and 19th centuries. There were many advantages and disadvantages of these atomic models. However, they played a crucial role in the evolution of the modern atomic model. Let’s learn how.
John Dalton, an English chemist, put forth that all matters are made up of atoms, which are invisible and unbreakable. The postulates of Dalton’s Atomic Theory are:
- Atoms are made up of matter.
- Atoms are invisible.
- Only one type of atom is present in specific elements.
- The constant mass of each atom varies from element to element.
- In the course of chemical reaction atoms experience rearrangement.
- These atoms can be modified but cannot be created nor can be destroyed.
Sir Joseph John Thomson conducted an experiment called the cathode ray experiment. He realized that through the experiment you can define the atomic structure as a positively charged sphere having negatively charged electrons in it. Thomson used a tube made of glass with two openings through which you can pump in the gas and another a vacuum pump to get the gas out. According to Thomson, atoms are electrically neutral as positive and negative charges have equal magnitude.
The limitation of the Thomson Atomic Model is that it failed to explain clearly the stability of an atom and that other subatomic particles cannot be deposited inside this model.
Rutherford altered the atomic structure with the discovery of subatomic particles called the nucleus. His experiment employed Alpha ray scattering. His observations were:
- The space inside the atom is empty.
- Due to repulsion, some rays get reflected as well, and because of the strong positive charge in the centre of the atom, 1/1000th rays got strongly deflected.
- The nucleus is occupied by the charge and mass of the atom.
- If electrons spend energy while revolving around the nucleus, then it will lose all their energy; thus, the stability of the atom is not described.
- If electrons revolve around the nucleus, then it will be a continuous spectrum. But in actuality, it is a line spectrum.
The Subatomic particles include:
- Protons: They are positively charged subatomic particles having a 1e charge and mass of roughly 1.672 × 10-24.
- Neutrons: The mass of neutrons is nearly the same as that of a proton, i.e. 1.674×10-24. Neutrons carry no charge and are electrically neutral particles.
- Electrons: It carries a charge of -1e and mass roughly 9.1 × 10-31. Electrons are disregarded while calculating the mass of an atom because of their relatively negligible mass.
Nucleons are the part of the nucleus of an atom. You can consider a nucleon as both a proton or a neutron. Atomic numbers illuminate the unique number of protons present in an element. However, an element’s atomic structure can differ in the total number of nucleons.
The variation of elements having different nucleon numbers is called isotopes of the elements. So if you find an element having the same number of protons but the number of neutrons being different then that will be an isotope of an element.
According to this theory proposed by Niels Bohr and Ernest Rutherford:
- The electrons inside atoms are placed in discrete orbits called stationary orbits.
- Quantum numbers represent the energy level of these cells.
- Electrons tend to jump to higher levels by absorbing energy and vice versa.
- Electrons spin around the nucleus in these stationary orbits only.
- Stationary orbits energy is quantified.
Thomas Young was the first to prove that electrons have a photoelectric effect which states that they also have wave nature. He showed that through an experiment called the double-slit experiment.
1. Who discovered the structure of the atom?
Answer: Democritus was the first to propose the concept of atoms, but the idea of atomic theory was revived by John Dalton.
2. What is the atomic structure in physics?
Answer: It is a complex arrangement of negatively charged electrons put in shells about a positively charged nucleus. Atom’s mass which is made up of protons and neutrons is the content of the nucleus. Neutrons proved to help understand the structure of an atom.
3. Who found Neutron?
Answer:- British physicist James Chadwick, discovered neutrons in 1932.
4. Who discovered the electron?
Answer:- In 1897, British physicist J.J. Thomson discovered electrons.
The study of the structure of atom has greatly aided in understanding the whole class of chemical reactions, bonds, and their physical properties. Therefore, it is crucial to learn the core concept behind the structure of atom. To learn more about it, check out the MSVgo app and their official site. The MSVgo philosophy is to enable a core understanding of any concept. The video library of the app explains concepts with examples or explanatory visualisations or animations., Happy learning.
- Some Basic Concepts of Chemistry
- Classification of Elements and Periodicity in Properties
- Chemical Bonding and Molecular Structure
- States of Matter: Gases and Liquids
- Chemical Thermodynamics
- Redox Reactions
- s -Block Elements
- p -Block Elements
- Organic Chemistry: Some Basic Principles and Techniques