NIOS Class 12 Chemistry Chapter 2 Atomic Structure

NIOS Class 12 Chemistry Chapter 2 Atomic Structure Solutions English Medium As Per New Syllabus to each chapter is provided in the list so that you can easily browse throughout different chapters NIOS Class 12 Chemistry Chapter 2 Atomic Structure Notes in English and select need one. NIOS Class 12 Chemistry Solutions English Medium Download PDF. NIOS Study Material of Class 12 Chemistry Notes Paper Code: 313.

NIOS Class 12 Chemistry Chapter 2 Atomic Structure

Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 12 Chemistry Notes, NIOS Senior Secondary Course Chemistry Solutions in English for All Chapter, You can practice these here.

Atomic Structure

Chapter: 2

Module – II: Atomic Structure and Chemical Bonding

INTEXT QUESTION 2.1

1. Compare the mass of an electron with that of the proton.

Ans: Proton is heavier than electron. 

The ratio of their masses is:

= mₚ/mₑ = (1.672 623 × 10⁻²⁷ kg) / (9.109 389 × 10⁻³¹ kg) 

= 1836.

2. What is a fundamental particle?

Ans: Main constituent particles like proton, neutron and electron etc. present in the atom come in the category of fundamental particles.

3. What is the name given to neutral particles in the atom?

Ans: Neutron.

INTEXT QUESTION 2.2

1. List the three constituent particles of an atom.

Ans: Electron, proton and neutron.

2. What was the aim of Rutherford’s α-rays scattering experiment?

Ans: The aim of Rutherford’s experiment was to test the Thomson’s plum-pudding model.

3. Briefly describe Rutherford’s model of an atom.

Ans: According to Rutherford’s model for atom, the positive charge of the atom and most of its mass is contained in the nucleus. The rest of the atom is empty space which contains the much smaller and negatively charged electrons.

4. On what basis was the Rutherford’s model rejected?

Ans: Rutherford’s model was rejected because it could not explain the stability of the atom.

INTEXT QUESTION 2.3

1. What is an electromagnetic radiation?

Ans: Electromagnetic radiation is a kind of energy which is transmitted through space in the form of electric and magnetic fields. It travels with the speed of light and does not need any medium to travel.

2. List any three characteristics of electromagnetic radiation.

Ans: The different characteristics of electromagnetic radiation are:

(i) Amplitude.

(ii) Wavelength.

(iii) Frequency.

(iv) Wave number and.

(v) Velocity.

3. What is wave number? How is it related to wave length?

Ans: The wave number is defined as the number of waves per centimeter. It is equal to the reciprocal of the wavelength.

4. What is the difference between a ‘quantum’ and a ‘ photon’?

Ans: A quantum of visible light is called photon. The energy of the quantum (or photon) is proportional to the frequency of radiation.

INTEXT QUESTION 2.4

1. What is the difference between a line spectrum and a continuous spectrum?

Ans: A line spectrum consists of a series of discrete lines of characteristic wavelengths while a continuous spectrum contains a broad band of radiations containing all possible wavelengths in the range i.e., the wavelengths of the radiation varies continuously.

2. What are the main postulates of Bohr’s model?

Ans: The main postulates of Bohr’s model are:

(i) The electrons move in a definite circular paths called as stationary orbits or stationary states around a central stationary nucleus.

(ii) The electrons can change their orbits by absorbing or emitting a photon of energy (= hí) equal to the difference of the energies of the orbits.

(iii) The angular momentum of the electron is quantised.

3. How does the energy of a Bohr orbit vary with the principle quantum number ‘n’.

Ans: The energy of a Bohr’s orbit increases with an increase in the value of the principal quantum number, n. In fact it becomes lesser and lesser negative.

INTEXT QUESTION 2.5

1. What do you understand by wave-particle duality?

Ans: The wave-particle duality refers to the fact that light and the material particles like electrons could sometimes behave as a particle and as a wave at other times.

2. Name the experiment that established the wave nature of electron.

Ans: The wave nature of electron was established by the diffraction of electron waves by the crystal lattice of nickel.

3. Compute the de-Broglie wavelength associated with an electron moving with a velocity of 100 km /second? (mₑ= 9.1 x 10⁻³¹kg)

Ans: Mass of the electron = 9.1 × 10⁻³¹kg

Speed or Velocity = 100 kms⁻¹ = 10 ms⁻¹

Using equation , the wavelength associated with the electron will be:

λ = h/mv = (6.626 × 10⁻³⁴ J s) / (9.1 × 10⁻³¹kg) (10⁵ m s⁻¹) = 7.28 × 10⁻⁹m.

4. State Heisenberg’s Uncertainty Principle?

Ans: According to Heisenberg’s Uncertainty Principle it is not possible to measure both the position and momentum of a particle with any degree of certainty. More accurately we measure a particle’s position, the less accurately we are able to measure it’s momentum, and vice versa.