NEET Exam  >  NEET Notes  >  Physics Class 12  >  Atomic Masses and Composition of Nucleus

Atomic Masses and Composition of Nucleus | Physics Class 12 - NEET PDF Download

Nucleus

The entire positive charge and nearly the entire mass of atom is concentrated in a very small space called the nucleus of an atom.

Atomic NucleusAtomic Nucleus

The nucleus consists of protons and neutrons. They are called nucleons.

Terms Related to Nucleus:

(i) Atomic Number: The number of protons in the nucleus of an atom of the element is called atomic number (Z) of the element.

(ii) Mass Number: The total number of protons and neutrons present inside the nucleus of an atom of the element is called mass number (A) of the element.

(iii) Nuclear Size: The radius of the nucleus R ∝ A1/3

⇒ R = Ro A1/3

where, Ro = 1.1 * 10-15 m is an empirical constant.

(iv) Nuclear Density: Nuclear density is independent of mass number and therefore same for all nuclei.

ρ = mass of nucleus / volume of nucleus ⇒ ρ = 3m / 4π R3o

where, m = average mass of a nucleon.

(v) Atomic Mass Unit: It is defined as 1 / 12th the mass of carbon nucleus.

It is abbreviated as amu and often denoted by u. Thus

1 amu = 1.992678 * 10-26 / 12 kg

= 1.6 * 10-27 kg = 931 Me V

Question for Atomic Masses and Composition of Nucleus
Try yourself:
Which of the following terms refers to the number of protons in the nucleus of an atom?
View Solution

Isotopes:

The atoms of an element having same atomic number but different mass numbers are called isotopes.

e.g., 1H1, 1H2, 1H3 are isotopes of hydrogen.

Fig: Isotopes of hydrogenFig: Isotopes of hydrogen

Isobars:

The atoms of different elements having same mass numbers but different atomic numbers, are called isobars.

e.g., 1H3, 2He3 and 10Na22, 10Ne22 are isobars.

Isotones:

The atoms of different elements having different atomic numbers and different mass numbers but having same number of neutrons, are called isotones.

e.g., 1H3, 2He4 and 6C14, 8O16 are isobars.

Isomers:

Atoms having the same mass number and the same atomic number but different radioactive properties are called isomers.

Nuclear Force:

The force acting inside the nucleus or acting between nucleons is called nuclear force.

Nuclear forces are the strongest forces in nature.

  • It is a very short range attractive force.
  • It is non-central. non-conservative force.
  • It is neither gravitational nor electrostatic force.
  • It is independent of charge.
  • It is 100 times that of electrostatic force and 1038 times that of gravitational force.

According to the Yukawa, the nuclear force acts between the nucleon due to continuous exchange of meson particles.

Question for Atomic Masses and Composition of Nucleus
Try yourself:
Which of the following statements is true about isotopes?
View Solution

Mass Defect:

The difference between the sum of masses of all nucleons (M) mass of the nucleus (m) is called mass defect.

Mass Defect (Δm) = M – m = [Zmp + (A – Z)mn – mn]

Nuclear Binding Energy:

The minimum energy required to separate the nucleons up to an infinite distance from the nucleus, is called nuclear binding energy.

Nuclear binding energy per nucleon = Nuclear binding energy / Total number of nucleons

Binding energy, Eb = [Zmp + (A – Z) mn – mN]c2

Packing Fraction (P):

p = (Exact nuclear mass) – (Mass number) / Mass number

= M – A / M

The larger the value of packing friction. greater is the stability of the nucleus.

[The nuclei containing even number of protons and even number of neutrons are most stable.

The nuclei containing odd number of protons and odd number of neutrons are most unstable.]

The document Atomic Masses and Composition of Nucleus | Physics Class 12 - NEET is a part of the NEET Course Physics Class 12.
All you need of NEET at this link: NEET
105 videos|425 docs|114 tests

Top Courses for NEET

FAQs on Atomic Masses and Composition of Nucleus - Physics Class 12 - NEET

1. What is the atomic mass of a nucleus?
Ans. The atomic mass of a nucleus is the total mass of protons and neutrons present in the nucleus of an atom.
2. How is the composition of a nucleus determined?
Ans. The composition of a nucleus is determined by the number of protons and neutrons it contains, which are known as the atomic number and mass number respectively.
3. How do you calculate the atomic mass of an element using the composition of its nucleus?
Ans. The atomic mass of an element can be calculated by adding the number of protons and neutrons in the nucleus, multiplied by the mass of each particle.
4. Why is the composition of a nucleus important in understanding the properties of an element?
Ans. The composition of a nucleus determines the element's atomic number, which dictates its chemical properties, and the mass number, which affects its physical properties.
5. Can the composition of a nucleus change through nuclear reactions?
Ans. Yes, the composition of a nucleus can change through nuclear reactions such as fusion, fission, and radioactive decay, leading to the formation of different elements.
105 videos|425 docs|114 tests
Download as PDF
Explore Courses for NEET exam

Top Courses for NEET

Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev
Related Searches

past year papers

,

Viva Questions

,

Extra Questions

,

Free

,

Semester Notes

,

study material

,

Objective type Questions

,

Summary

,

Atomic Masses and Composition of Nucleus | Physics Class 12 - NEET

,

Atomic Masses and Composition of Nucleus | Physics Class 12 - NEET

,

Previous Year Questions with Solutions

,

ppt

,

practice quizzes

,

mock tests for examination

,

Important questions

,

Exam

,

Sample Paper

,

shortcuts and tricks

,

pdf

,

video lectures

,

MCQs

,

Atomic Masses and Composition of Nucleus | Physics Class 12 - NEET

;