The Structure of an Atom

At the end of the article, you will able to Explain the Structure of an Atom. Let’s start discussing it. We all already know that a matter is any substance which has mass and occupies space. All the objects we see around us such as a book, your pen or pencil also natural things like such as rocks, water, and plants are the part (subject) of the universe. You should always remember that a matter is made up of atoms.

The structure of an atomDescribe the Structure of an Atom

Structure: Atoms are composed of electron, proton, neutron and various smaller particles that lies within the nucleus. The smallest indivisible particle of matter is an atom. Three important particles are

  • Electron
  • Proton and
  • Neutron

These particles are main constituents of the atom so that is why we call as fundamental particles. The electrons present around the atom are attracted to the protons. These protons are present in an atomic nucleus. The force with which these electrons are attracted is an electromagnetic force. The protons and neutrons also attract each other in the nucleus. But this force is called as the nuclear force.


  1. Symbol -P+
  2. Mass -1836(9.1×10-31)Kg
  3. Charge -+1.6 × 10-19C


  1. Symbol -N0
  2. Mass -1836(9.1×10-31)Kg
  3. Charge -Zero


  1. Symbol – e
  2. Mass -9.1×10-31Kg
  3. Charge -(minus)1.6 × 10-19C
  • The charge magnitude of Electron and Proton are same.
  • Neutron has no charge.
  • An electron has a negative charge.
  • Proton has a positive charge.
  • overall nucleus has a positive charge.
  • The whole atom is electrically neutral.

These particles are countless in any substance. It is impossible to measure the exact number of atoms in a given kilograms. An approximation was given by the scientist Avogadro stating the new measurement to count named mole. Let’s describe the structure some more.

Explain the Properties of Atom

  • Dalton, in 1808, proposed that atoms are very very small, inseparable particles.
  • Atoms are tasteless and colorless.
  • An atom is electrically neutral.
  • The number of protons and neutrons together decide mass of an atom.
  • The number of atoms before and after the reaction remains the same.
  • Atom is the smallest particle of an element that participates in the chemical reaction.
  • When the group of atoms gets together may be same or different types we call as a molecule.
  • The size atom varies between .3 Å(1angstrom=1010 m) to 3 Å.
  • Atom is the smallest particle of an element that retains all its properties and enters into a chemical reaction.

The various scientists describe the structure of the atom with their own theories.

Structure Explanation
Thomson Model of Atom Model of an atom is also called plum pudding or raisin pudding model.
Rutherford’s Model The model is also called solar or planetary model of an atom. This model was base upon the results of ∝- scattering experiment.
Bohr Atomic Model The electrons keep on revolving in circular orbit around the nucleus. There is no loss or energy during circular motion

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History of the Atom

The concept of explaining the structure was given by the three scientists. Out of which Neil Bohr successfully describe the Structure of an Atom.  A comparison between the different models proposed by the three scientist JJ Thomson, Rutherford and Neil Bohr is given below:Describe the Structure of an Atom

J J Thomson Atomic Theory

Ernest Rutherford Atomic Theory

Neils Bohr Atomic Theory

An atom consists of a ball. positive charge(+) and electrons(-) are embedded like a seed. The number to the total positive charge equals to the negative charge due to which atom has no charge.It means atoms are electrically neutral He defines the structure of atom as- An atom consists of the positively charged nucleus at the center. Electrons revolve around the circular path with a very high speed. There exists an electrostatic force between the proton and the negative charge electron which keep the atom hold together. The number of protons is equaled to the number of negative electrons. Due to which atom is electrically neutral. Almost entire mass is in the nucleus. Most of the atom is empty space. Bohr model of atom states that an atom is made up of three particles electron, proton, neutron. An electron has a negative charge, proton having a positive charge while the neutron has no charge.   Electrons revolve in a fixed energy level donated as 1,2,3,4,5,6 or by letter K, L, M, N, O, P counted from the centre to outward.

Basic Structure of an Atom

After the above discussion. It time to explain more basic concepts that students often get confused. It generally happens when attempting worksheet or a question asked by the teacher.Basic Structure of an Atom

The basic structure of an atom has a wide variety of questions that need to consider. Let’s start it one by one.

Q- Name the subatomic particles of an atom?

Ans-Electron, proton, and neutron.

Q- Name the scientist who first formulated the basic structure?

Ans-John Dalton, a British teacher in 1808 first proposed a firm scientific basis known as
Dalton’s atomic theory.

Q- Which experiment led to the discovery of electrons?

Ans-The cathode ray discharge tube experiment performed by J.J. Thomson led to the
discovery of negatively charged particles called an electron.

Q-Name the scientist who first gave the atomic model.

Ans- J.J. Thomson, in 1898 first proposed the atomic model called raising-pudding model.

Q-  What is an isotope?

Ans-Atoms of the same elements having a same atomic number but a different mass number
are called isotopes. For Examples –126C,136C,146C

Q- What are isobars?

Ans-Atoms of different elements which have the same mass number but different atomic nos. For example- 146147N.

Q- What are isotones?

Ans- Atoms of different elements which contains the same number of neutrons.

Q- What is an atomic number?

Ans- Atomic number is defined as the number of protons presents in the nucleus of an atom or the number of electrons present in a neutral atom of an element.

Q- What is a mass number?

Ans-Maas number of an element is the number of proton and neutron present in the nucleus of an atom.

Q- Find out the atomic number, mass number, number of electrons and neutrons in an element 4020 X?

The mass no. of X is 40
The atomic no. of X is 20
No. of proton is = Z -A = 40 – 20 = 20

These are the questions of the Basic Structure of an Atom.

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