Page 1 - 4.HOME ASSIGNMENT-(AOMIC NUMBER AND MASS NUMBER)

SAI International School
Class-IX
Subject-Chemistry
Topic-Structure of atom
Sub topic- Atomic number and mass number
OBJECTIVE QUESTIONS
Q.1 Assertion: Mass number of calcium is 40.
Reason: Calcium atom has 20 protons and 20 neutrons.
Q.2 Assertion: Sodium atom has 11 electrons.
23
Reason: Sodium atom can be represented as 11Na .
Q.3 Assertion: Mass number of Argon is 40.
Reason: Sum of the nucleons in Argon atom is 40.
Q.4 Assertion: The mass number of Carbon is 6.
12
Reason: Carbon atom can be represented as 6C .
Q.5 Assertion: Atomic mass number of Phosphorous is 31.
Reason: One atom of Phosphorous weighs 31 g.
Q.6 In Bohr’s model how do electrons travel?
a) Electrons move in and out of the nucleus.
b) Electrons do not move
c) Electrons move in circular paths called orbits around the nucleus.
d) Electrons move in the straight line.
Q.7 In the nucleus of 20Ca , there are
40
a) 40 protons and 20 electrons
b) 20 protons and 40 electrons
c) 20 protons and 20 neutrons
d) 20 protons and 40 neutrons
Q.8 Which pair of atom contains the same number of neutrons?
a) 43Cd 114 & 50Sn 119
b) 27Co & 28Ni
59
59
c) 55Cs 133 & 54Xe 132
d) 29Cu & 29Cu
65
63

SUBJECTIVE
Sl.No. Questions Mark
31
Q.1 Find the number of neutrons in 15X . 1

Q.2 What is meant by nucleons? 1

Q.3 The atomic number and mass number of an element are 16 and 32 3
respectively. Find the number of protons, electrons and neutrons in
it.?
32
Q.4 2. From the symbol16S , give 3
a) The atomic number
b) The mass number.
c) The number of protons, neutrons and electrons
Q.5 a) The composition of nuclei of two atomic species X and Y are given 5
below-

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