Class 12 Physics Ch 12

Atoms CBSE Class 12 Physics Chapter 12 Notes

Class XIIth Notes Atoms Chapter 12 Notes Class 12th Physics Notes , CBSE Chapter 12 Atoms Class 12 Solutions Physics in PDF are free to download from the PW PhysicsWallah . Atoms class 12 Solutions Physics latest chapter wise notes for speedy preparation of CBSE board exams and school-based yearly examinations are now available in the finest app for CBSE students. Class 12 Physics notes for Chapter 12 Atoms Revision Notes and Formulas can also be downloaded from the CBSE Guide website.

Notes for CBSE Atoms Class 12 Physics
CBSE guide notes are comprehensive notes that cover the most recent CBSE and NCERT syllabuses. It covers all of the topics included in the NCERT Class 12 Physics textbook. CBSE guide rapid revision notes can be downloaded through below link

CBSE Class 12 Physics Ch 12 Atoms Notes

 The NCERT Results for Class 12 physics are matter experts according to the latest CBSE Syllabus 2023-24 and its marking schemes. Chapter 12 Atoms covers all of the major subjects in detail, allowing students to better understand the ideas. Students studying for their Class 12 exams should consult NCERT Solutions for Class 12 Physics Chapter 12 Atoms. We will look at many atomic models in this chapter. Initially, J.J. Thomson developed an atomic model in which electrons were considered to be lodged between protons. On the basis of a scattering experiment, his pupil Earnest Rutherford presented a nuclear model in 1911. Despite substantial experimental evidence, Rutherford's model of the atom was rejected on the basis of classical electromagnetic theory.

To address the inadequacies of Rutherford's model, Niels Bohr merged Einstein's classical and early quantum conceptions with those of Plank in 1913 to explain the stability of an atom.



1. All elements consist of small, invisible particles called atoms.  Each atom is a radius of 10 to 10 m, in which the entire mass is distributed uniformly and the negatively charged electrons revolve around the nucleus.
  2. Experimental arrangement of the dispersion experiment and α path followed by α molecules

  3. The effect parameter is the vertical distance of the velocity vector of particle A from the central line of the atomic nucleus. The effect parameter (b).

  Where, K is the KE of the alpha particle, θ the dispersion angle, Z is the atomic number of the nucleus and e is the nucleus charge.
  4. The basic assumption of Rutherford's atomic model
  (I) The atom is made up of a small central nucleus, called the atomic nucleus, where the entire mass and positive charge are supposed to be concentrated.
  (ii) The nucleus is much smaller than the size of an atom.
  (3) The nucleus is surrounded by electrons and the atom is electrically neutral.
  (4) The electrons revolve around the nucleus and the center force is of an electrostatic nature.
  5. The closest approaching distance at a certain distance r0 from the nucleus, the entire KE converts from the α particle to electrostatic energy and the α particle cannot come closer to the nucleus, this distance (r0) is called the closest approach distance.

  6. The angle of dispersion An angle called the deviation of a particle from its original path around the nucleus called the angle of dispersion.
  7. Disadvantages of the Rutherford model
  (I) The stability of the atom cannot be clearly explained.
  (2) Unable to explain the spectrum of the line.
  8. Bohr's hydrogen theory Atom Bohr combined early quantum and classical concepts and gave his theory in the form of three axioms.  here they are
  (I) Bohr's first assumptions were that an electron in an atom could orbit in certain stable orbits without emitting radiant energy, contrary to the forecasts of the electromagnetic theory.
  (Ii) Bohr's second assumption defines these stable orbits.  This hypothesis states that the electron orbits only around the nucleus in those orbitals for which the angular momentum has an integral multiple of h / 2π, where h is Planck's constant (= 6.6 × 10-34 J - s).  Thus, the angular momentum (L) of the orbital electron is
  Quantified, i.  e.  L = nh / 2π
  Also, the angular momentum of the electron (L) = mvr
  ∴ For any permissible (stationary) orbit, mvr = nh / 2π
  Where n = any positive integer, i.e. 1, 2, 3, ...
  It is also called the base quantum number.
  (Iii) Bohr's third hypothesis assumes that the electron may travel from its specific non-radioactive orbits to ones with less energy.  When it does, the photon emits an energy equal to the energy difference between the initial and final states.
  The frequency of the photon emitted is then given by
  hv - Ei– Ef
  Whereas, Ei and Ef are the primary and final states energies and Ei> Ef.
  9. Limits of the Bohr model
  (I) It applies only to hydrogen as the atom.
  (2) does not explain the exact structure of the spectral lines in the H atom.
  (Iii) does not explain the shape of the orbit.
  10. The following are the important formulas related to the Bohr model for hydrogen atoms:


  11. Energy level The energy of an atom is the lowest when its electron orbits in an orbit close to the nucleus, that is, n = 1.
  12. The minimum state of an atom is called the ground state. This state has the lowest energy.  The power of this case is -13.6V.  Therefore, the minimum energy needed to free an electron from the ground state of a hydrogen atom is -13.6V.
  13. (i) Emission spectrum The hydrogen spectrum is composed of separate bright bright lines
  The background is known specifically as the hydrogen emission spectrum.
  (ii) Absorption spectrum There is another type of hydrogen spectrum where we get dark lines on the bright background, known as the absorption spectrum.
  14- Atomic hydrogen is emitted from a linear spectrum consisting of different chains. 

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Class 12 physics Chapter 12 Atoms Notes is an important study material for the Students who are presently studying in CBSE 12th standard. The NCERT Results for Class XIIth physics
The PW PhysicsWallah offers free PDF downloads of Class 12 Physics Chapter 12 Atoms Notes. These latest chapter-wise notes are ideal for quick preparation of CBSE board exams and school-based annual examinations. Additionally, CBSE Guide website provides comprehensive notes covering the latest syllabus of CBSE and NCERT, including all topics given in NCERT class 12 Physics textbook. Users can download CBSE guide quick revision notes from both platforms to score high in exams.

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