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NCERT Books for Class 12 Physics Chapter 12 - Atoms Free PDF Download

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Free NCERT Books download for Class 12 Physics Chapter 12 - Atoms on Vedantu.com. Students can also download the NCERT Textbooks Solutions in PDF for Class 6 to 12 all subjects. Register for Physics tuition to clear your doubts and score more in your exams.


Question: How to download Class 12 Physics Chapter 12 NCERT Book for CBSE?


Answer: Students can download it from Vedantu. On this page, Students can download Class 12 Physics Chapter-12 PDF Solutions of the Book.

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Class 12 Physics Chapter 12 NCERT Books - Atoms

Atoms are the basic unit of an element. It is a tiny particle that cannot be cut into smaller parts and exist as a part of that element. One atom contains an equal number of electrons and protons. Atoms have no definite size because even if you try, you can never isolate one from another without using any external energy. The smallest part into which any element can be broken into is called an atom. Atoms are the smallest particle of an element that maintains all the properties of that element. For example, oxygen is an element, and it has some specific characteristic properties as It glows in the dark: This means that when electrons collide with each other and produce visible energy colour to the flame: This means that when you burn fuel, the heat produced from the burning of the fuel causes electrons to collide with each other and produces energy which we can see as light. In this case, oxygen has a role in producing light from the burning of fuel. In water, when oxygen combines with two hydrogen atoms, it forms the water molecule. The reaction between oxygen and hydrogen is exothermic, i.e., energy is produced in this reaction. 


When electrons combine to form the water molecule, then how do electrons separate? When we dissolve something in the water, what happens? The molecules which are formed are the solution. When we dissolve oxygen in water, electrons of water molecules get attracted towards it and start moving around it. The net result of this action is that the dissolved oxygen remains present everywhere in the water but as a single molecule (O2). Hence, such reactions to form solute and solvent also give rise to energy.

FAQs on NCERT Books for Class 12 Physics Chapter 12 - Atoms Free PDF Download

1. How are atoms formed? 

The old-age theory about the origin of an atom was that atoms are formed when all the planets in our universe collide with each other. This is called 'Big Bang Theory. But now, two theories are proposed to explain the formation of atoms..1) 'Plasma Theory'.2) 'Continuous Spontaneous Generation theory

  • Plasma Theory: According to this theory, at the beginning of the universe, all matter existed as plasma. A plasma is a gas in which some of its atoms are ionized to produce electrical currents.

  • Continuous Spontaneous Generation theory: According to this theory, there is no end to the universe, and everything is in a continuous process. One part of the plasma becomes dense and collapses, which forms a star system with all planets orbiting around it. This collapse may form the sun or the stars etc. In such stars, atoms are formed when a helium nucleus collides with a hydrogen atom.

2. What are the types of Atoms?

There are two types of atoms. One is the natural atom, and another one is an artificial atom that can be artificially produced by us. Artificial atoms are also called 'artificial molecules'.We can define artificial atoms or artificial molecule in terms of how it reacts with other things like-

  • It reacts with only some specific type of elements

  • It cannot react with anything else apart from a small range of elements

  • It reacts with a large number of elements. For example, in H2, the element 'hydrogen' is an artificial atom as it can only react with other atoms, which are also hydrogen. On the other hand, SO4 is not an artificial atom as it reacts with many types of elements.

3. What is the significance of an atom? What role does it perform?

An atom performs four roles in its life-

  • It helps in changing the chemical environment of other atoms.

  • The electrons inside it help in transferring energy from one atom to another atom.

  • The protons and neutrons inside it provide a place for other atoms to attach to.

  • Protons and neutrons provide a nucleus for maintaining the shape of the atom. 


Hence, we see that all atoms in our body are interacting with each other, and hence they can never remain as isolated entities. Hence, it is always better to say 'Atoms interact'. Vedantu provides free physics tuition for students after class 12th. Register at vedantu.com to get free online tuitions, study material, and NCERT solutions of Class 6 to 12 Physics.

4. How are atoms separated?

When you dissolve something in the water, what actually happens is that particles of atoms break down into small enough parts so that they merge with the water molecules. The atoms are so small that they cannot be seen with the naked eye. When you mix two or more types of solute, then it is very difficult to separate the resulting mixture into its original parts as they have now formed new molecules which can only be separated by breaking covalent bonds, ionic bonds etc.

5. How big is an atom?

An atom has a very small size, yet it contains many things within itself, such as protons, neutrons, electrons, and an atomic nucleus. Atoms are not seen by the human eyes and cannot also be touched. A microscope is mostly used to observe them. An atom contains protons, electrons and neutrons. Protons are positively charged particles with a mass nearly 2 000 times greater than the mass of electrons. Neutrons are neutral particles with a mass nearly 2000 times greater than electrons. An atom contains 99.95% space, i.e., only 0.05% content consists of protons, electrons and neutrons that can be observed by instruments like microscopes etc.