class 9 chemistry chapter 4 --- the structure of atom practice sheet
CLASS: IX; CHEMISTRY
CHAPTER-4
THE STRUCTURE OF ATOM
Q1 Write down the two main postulates of Bohr's
model of an atom.
Q.2 What are Energy levels or Shells ?
Q.3 How are
electrons distributed in different orbits or shells according to Bohr-Bury
scheme?
Q.4 Who discovered
neutrons? How is a neutron represented? Write its charge and mass.
Q.5 NCERT
Pg.49
Helium atom has an atomic mass of 4u and two
protons in its nucleus. How many neutrons does it have?
Q.6 NCERT Pg.50
Draw the Bohr's model to represent the
distribution of electrons in (a) Carbon (ii) Sodium
Q.7 NCERT
Pg.50
If K and L shells
of an atom are full, what would be the total number of electrons in the atom?
Q.8 Draw table 4.1
or stick a printout.
Q.9 Define valency
. How is valency calculated? Calculate the valency of (a) Sodium (b) chlorine
(c) Neon
Q.10 Define Octet.
How do atoms attain an octet?
Q.11 What is
atomic number?
Q.12 How is the mass of an atom calculated? Write down the term used to represent this
mass.
Q.13 Write the
general notation of an atom when atomic mass and atomic number is given.
Q.14 Write down
the notation of all the elements from 1 to 20 by referring to the atomic mass
and atomic number from table 4.1.
Q.15
NCERT Pg 52
If number of
electrons in an atom is 8 and number of protons is also 8
(i) What is the
atomic number of the atom (ii) What is the charge on the atom.
Q.16 Differentiate
between Isotopes and Isobars with examples.
Q.17
NCERT Pg 53 For the symbol
H,D, and T ,tabulate three subatomic particles found in each of them.
Q.18
NCERT Pg 53Write the
electronic configuration of any one pair of isotopes and isobars.
Q.19 Write down
any three applications of isotopes.
Q.20 If an atom
has isotopic forms , how is the mass of the atom calculated?
Q.21NCERT Pg 54 Compare
the properties of electrons, protons and neutrons.
Q.22 NCERT Pg 54
Summarise the rules
for writing of distribution of electrons in various shells for the first
eighteen elements.
Q.23 NCERT
Pg 54 Define valency by
taking examples of silicon and oxygen.
Q.24 NCERT Pg 54 Compare all the proposed Bohr’s models of an
atom given in this chapter.
Q.25 NCERT Pg 55 Na+ has completely
filled K and L shells. Explain.
Q.26 NCERT Pg 55
If
bromine atom is available in the form of say, two isotopes 7935Br
(49.7%) and 8135Br (50.3%), calculate the average
atomic mass of bromine atom.
Q.27 NCERT Pg 55
The
average atomic mass of a sample of an element X is 16.2 u. What are the
percentages of isotopes 168X and 188X
in the sample?
Q.28 NCERT Pg 55
If Z
= 3, what would be the valency of the element? Also, name the element.
Q.29 NCERT Pg 55
Composition of the nuclei of two atomic
species X and Y are given as under
X – Y Protons
=6, 6
Neutrons = 6 ,8
Give the mass number of X and Y. What
is the relation between the two species?
Q.30 NCERT Pg 55
For
the following statements, write T for True and F for False.
(a) J.J. Thomson proposed that the nucleus of an atom contains only
nucleons.
(b) A neutron is formed by an electron and a proton combining together.
Therefore, it is neutral.
(c) The mass of an electron is about 1/2000 times that of proton.
(d) An isotope of iodine is used for making tincture iodine, which is
used as a medicine.
Put tick
against correct choice and cross (x) against wrong choice
Q.31 NCERT Pg 55
Rutherford’s alpha-particle scattering
experiment was responsible for the discovery of
(a) Atomic nucleus (b)Electron (c) Proton
(d)neutron
Q.32 NCERT Pg 55
Isotopes of an element have
(a) the same physical properties (c) different number of neutrons
(b)different number of neutrons (d) different atomic numbers.
Q.33 NCERT Pg 55
Number of valence electrons in Cl -
ion are :
(a) 16 (b) 8
(c) 17 (d) 18
Q.34 NCERT Pg 55
Which
one of the following is a correct electronic configuration of sodium?
(a) 2, 8 (b) 8, 2, 1
(c) 2, 1, 8 (d) 2, 8, 1
Q.35
NCERT Pg 56
Complete the following table.
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