Atomic Structure for MPSC State Exam - MPSC Study Notes for Chemistry

By Ganesh Mankar|Updated : May 22nd, 2022

Atomic structure is an important topic in chemistry. Questions are asked in all MPSC exams on this topic. In today's article, we will look at detailed information about Atomic structure.This topic is very important for the MPSC State Services Prelims Exam, MPSC Combined prelims exam as well as Maharashtra Police Recruitment etc.

Atomic Structure

Historical Background

Maharshi Kanad (600 BC)

  • He said that matter is made up of very small particles.
  • They called it 'Parmanu'/'परमाणु'.


  • The theory was proposed in 430 BC.
  • He said that all matter is made up of very small particles.
  • He called that particle 'atoms'.

John Dalton

  • In 1808, he proposed his theory.
  • All matter is made up of small particles, called atoms.
  • An atom cannot be created or destroyed.

Drawback: According to these three theories, it is not possible to say about the charge and particle in an atom.

J. J. Thomson

  • In 1867, he proposed his model of an atom.
  • He discovered the inner particle of an atom.
  • He compared an atom to a watermelon. Where he considered: 1. The red part of the watermelon as positively charged. 2. Watermelon seeds as negatively charged particles, embedded in them.
  • He said that an atom resembles a sphere of positive charge with electrons (negatively charged particles) present inside the sphere.

Drawback: Positive charge is scattered all over the atom and negative charge is scattered in it. Thomson was wrong to say this.

Ernest Rutherford

  • In 1911, he proposed his theory.
  • He compared an atom to a solar system. In it, the sun is the nucleus and the planet is the election.
  • An atom is hollow.
  • The midpoint of an atom is called the nucleus.
  • All the mass of the atom is contained in the nucleus.
  • Electrons move in a circular path outside the nucleus.

Drawback: Rutherford could not say that the electron rotates in a certain orbit.


1.     Nucleus

  • Discovered by Rutherford.
  • Atoms contain protons and neutrons.

2.     Orbit

  • Orbits contain electrons and positrons.

Atomic Number

  • The number of protons or electrons in an atom is called the atomic number.
  • Atomic numbers are denoted by the letter 'Z'.
  • g. A carbon atom has 6 protons and 6 electrons. So the atomic number (Z) of carbon is 6.

Atomic mass number

  • The complete amount in the protons and neutrons in the nucleus of an atom.
  • Atoms contain particles like Protons, Neutrons & Electrons. But since the mass of the electron is very small, only the mass of the protons and the neutrons are taken into account while measuring the mass of the atom.
  • The combined number of protons and neutrons in an atom is the atomic mass.
  • Molecules are denoted by the letter 'A'.

Atomic Mass (A) = atomic number (Z) + n

Neutron = Atomic Mass (A) - Atomic Number (Z)

  • E.g. The atom of carbon has 6 protons and 6 neutrons, so the atomic mass (A) of carbon is 6 + 6 = 12.

Molecular mass

  • Molecular mass is the sum of the aggregate masses of atoms in a molecule.
  • Example-H_2_O
  • Note: The hydrogen atom has 1 proton & 0 neutrons, so H has a molecular mass of 1.


      Niels Bohr

  • He said that electrons move in a fixed orbit, with a certain energy, at a certain speed.
  • There is a hollow space between the two chambers, the electron only found in orbit.
  • He named these shells K, L, M, N in ascending order of energy level.
  • The ability to accommodate electrons in each shell is different and specific.
  • Formula to fill the electron in the orbit:2n^2
  • Shell =  (n = Orbit number)

K=2X(1)^2 = 2
L=2X(2)^2 = 8
M=2X(3)^2 = 18
N=2X(4)^2 = 38

To know more about this topic, download the PDF, click here:

Atomic Structure, Download PDF in English

To access the content in Marathi, click here:


More From Us:

MPSC Current Affairs 2021: Download in Marathi & English

MPSC GK Study Material: Complete Notes for MPSC Exam [Free]

NCERT Books for MPSC State Exam 2021

Maharashtra Police Bharti 2021 Exam: Complete Study Material/संपूर्ण अभ्यास साहित्य  

byjusexamprep Daily, Monthly, Yearly Current Affairs Digest, Daily Editorial Analysis, Free PDF's & more, Join our Telegram Group Join Now


write a comment


  • The MPSC state service pre-examination consists of about three to four questions on chemistry.

  • The MPSC Combined Prelims Exam consists of 2-3 questions on the subject of chemistry

  •  Yes! In Maharashtra Police recruitment, there are one to two questions on the subject of Chemistry

  • Eighth, ninth, tenth standard science books should be read for the subject of physics.

  • The main examination of MPSC PSI / STI / ASO does not have questions on the subject of Science.

Follow us for latest updates