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Uestions: 4.3 How Are Electrons Distributed in Different Orbits (Shells) ?

The document discusses Bohr's model of the atom, which introduces the concept of discrete orbits for electrons that do not radiate energy while in these orbits. It also mentions the discovery of neutrons by J. Chadwick in 1932, highlighting their neutral charge and presence in atomic nuclei. Additionally, the document outlines the distribution of electrons in different energy levels as suggested by Bohr and Bury.

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Anjali Singh
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35 views1 page

Uestions: 4.3 How Are Electrons Distributed in Different Orbits (Shells) ?

The document discusses Bohr's model of the atom, which introduces the concept of discrete orbits for electrons that do not radiate energy while in these orbits. It also mentions the discovery of neutrons by J. Chadwick in 1932, highlighting their neutral charge and presence in atomic nuclei. Additionally, the document outlines the distribution of electrons in different energy levels as suggested by Bohr and Bury.

Uploaded by

Anjali Singh
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Q

4.2.3 BOHR’S MODEL OF ATOM uestions


In order to overcome the objections raised 1. On the basis of Thomson’s model
against Rutherford’s model of the atom, of an atom, explain how the atom
Neils Bohr put forward the following is neutral as a whole.
postulates about the model of an atom: 2. On the basis of Rutherford’s
(i) Only certain special orbits known as model of an atom, which sub-
discrete orbits of electrons, are allowed atomic particle is present in the
inside the atom. nucleus of an atom?
(ii) While revolving in discrete orbits the 3. Draw a sketch of Bohr’s model
electrons do not radiate energy. of an atom with three shells.
4. What do you think would be the
observation if the α -particle
Neils Bohr (1885-1962) scattering experiment is carried
was born in Copenhagen out using a foil of a metal other
on 7 October 1885. He was than gold?
appointed professor of
physics at Copenhagen 4.2.4 NEUTRONS
University in 1916. He got
In 1932, J. Chadwick discovered another sub-
the Nobel prize for his work
atomic particle which had no charge and a
on the structure of atom in
mass nearly equal to that of a proton. It was
1922. Among Professor
eventually named as neutron. Neutrons are
Bohr’s numerous writings, three appearing
present in the nucleus of all atoms, except
as books are:
hydr ogen. In general, a neutron is
(i) The Theory of Spectra and Atomic represented as ‘n’. The mass of an atom is
Constitution, (ii) Atomic Theory and, therefore given by the sum of the masses of
(iii) The Description of Nature. protons and neutrons present in the nucleus.

uestions

Q
These orbits or shells are called energy
levels. Energy levels in an atom are shown in 1. Name the three sub-atomic
Fig. 4.3. particles of an atom.
2. Helium atom has an atomic mass
of 4 u and two protons in its
nucleus. How many neutrons
does it have?

4.3 How are Electrons Distributed


in Different Orbits (Shells)?
The distribution of electrons into different
orbits of an atom was suggested by Bohr and
Bury.
Fig. 4.3: A few energy levels in an atom The following rules are followed for writing
the number of electrons in different energy
These orbits or shells are represented by levels or shells:
the letters K,L,M,N,… or the numbers, (i) The maximum number of electrons
n=1,2,3,4,…. present in a shell is given by the

STRUCTURE OF THE ATOM 49

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