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Structure of atoms class9 Multiple Choice questions






Given below are the CBSE Structure of atoms class9 Multiple Choice questions

Multiple Choice Questions:


1.When a B-particle is emitted, the atomic number of daughter element is one unit more as compared to that of parent element. This increase in atomic number is due to:
a)Addition of a proton to the nucleus
b)Removal of an electron from the nucleus
c)Decay of neutron present in the nucleus
d)Any one of the above
2.What is an electron?
a)A wave
b)A particle
c)Either of two, depending on how it is observed
d)Neither of these
3.The work function of a metal is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from the metal is approximately:
a)540nm
b)400 nm
c)300 nm
d)220 nm
5.The cathode ray experiment was done for the first time by:
a)J.J. Thomson
b)John Dalton
c)Goldstein
d)Rutherford
6.The charge on an electron is:
a)1.6 x 10-6 coulombs
b)1.6 x 10-20 coulombs
c)1.6 x 10-19 coulombs
d)1.6 x 10-16 coulombs
7.The nucleus of an atom contains:
a)Protons
b)Electrons
c)Protons and neutrons
d)Neutrons
8.By whom was neutron discovered?
a)Bohr
b)Chadwick
c)Rutherford
d)Dalton
9.In an atom valence electron are present in:
a)Outermost orbit
b)Next to outermost orbit
c)First orbit
d)Any one of its orbit
10.The maximum number of electrons that can be accommodated in third shell ( n = 3) is:
a)2
b)8
c)18
d)10
11.In an atom, the constituent electrons:
a)Do not move
b)Are uniformly distributed
c)Move around the nucleus in fixed energy levels.
d)Move around the nucleus in a random way.
12.What is the number of valence electrons of AI?
a)1
b)2
c)3
d)4
13.Which of the following arrangements of electrons represent magnesium (Mg)?
a)2, 8, 1
b)2, 8, 2
c)2, 8, 3
d)2, 8, 4
14.Which of the following statements s incorrect for cathode rays?
a)They move in straight line
b)Their nature depends upon the nature of gas present in the discharge tube.
c)They cost shadow of solid objects placed in their path
d)They get deflected towards positive charge.
15.The isotopes of an element have:
a)Same number of neutrons
b)Same atomic number
c)Same mass number
d)None of these
16.Which of the following statements is not correct for Bohr’s model of an atom?
a)The nucleus of an atom is situated at ts centre
b)The electrons move in circular orbits
c)Electrons jumps from one orbit to another
d)An electron neither loses nor gains energy it jumps from one orbit to another.
17.The atomic number of an element is 11 ad its mass number is 23. The correct order representing the number of electrons, protons and neutrons respectively in this atom is:
a)11, 11, 12
b)11, 12, 11
c)12, 11, 11
d)23, 11, 23
18.Which of the following pairs are isotopes?
a)Oxygen and ozone
b)Ice and steam
c)Nitric oxide and nitrogen dioxide
d)Hydrogen and deuterium
19.Which of the following have equal number of neutrons and protons?
a)Hydrogen
b)Deuterium
c)Fluorine
d)Chlorine
20.The number of electrons in an element with atomic number X and atomic mass Y will be:
a)(X – Y)
b)(Y – X)
c)(X + Y)
d)X
21.The relative aomic masses of many elements are not whole numbers because:
a)They cannot be determined accurately
b)The atoms ionize during determination of their masses
c)Existence of isotopes
d)Presence of impurities

23.Which of the following has a charge of +1 and a mass of 1 amu?
a)A neutron
b)A proton
c)An electron
d)A helium nucleus
24.Which of the following describes an isotope with a mass number of 99 that contains 56 neutrons in its nucleus?
a)99/56Ba
b)43/56Ba
c)99/43Tc
d)56/43Tc
25.Which of the following isotopes is used as the standard for atomic mass?
a)12C
b)16O
c)13C
d)1H
26.Which f the following is not a basic particle of an element?
a)An atom
b)A molecule
c)An ion
d)None
27.Which would be the electrical charge on a sulphur atom containing 18 ellectrons?
a)2-
b)1-
c)0
d)2+
28.Which of the following pairs are isotopes?
a)Oxygen and ozone
b)Ice and steam
c)Nitric oxide and nitrogen dioxide
d)Hydrogen and deuterium
29.Members of which of the following have similar chemical properties?
a)Isotope
b)Isobars
c)Allotropes
d)Both isotopes and allotropes
30.A natural phenomenon that supports the experimental conclusion that atoms are divisible is:
a)Allotropy
b)Radioactivity
c)Cracking
d)None of these
31.Aluminum has a valence of 3 and sulphate has valence of 2. Therefore, the correct formula for aluminum sulphate is:
a)AI2S2O4
b)AI2 (SO4)3
c) AI3 (SO4)2
d) AISO4
32.The correct representation of 3 molecules of chlorine is:
a)6 CI
b)3 Cl2
c) 2Cl3
d) Cl6
 
33.While performing cathode ray experiments, it was observed that there was no passage of electric current under normal conditions. Which of the following can account for this observation?
a)Dust particles are present in air
b)Carbon dioxide is present in air
c)Air is a poor conductor of electricity under normal conditions
d)One of the above
34.The fluorescence on the walls of discharge tube is due to:
a)Cathode rays
b)Anode rays
c)Canal rays
d)None of the above
35.Which of the following electronic configurations is wrong?
a)Be (3) = 2, 1
b)S (16) = 2, 6, 8
c)P (15) = 2, 8, 5  

36.55/25Mn++ has:
a)25protons and 30neutrons
b)25neutrons and 25protons
c)25electrons and 40 protons
d)None of the above

37.Which one of the following statement is not true?
a)Most of the space in an atom is empty
b)The total number of neutrons and protons is always equal in a neutral atom
c)The total number of electrons and protons in an atom is always equal
d)The total number f electrons in any energy level can be calculated by the formula 2n2
38.17CI35 and 17CI37 are examples of:
a)Isobars
b)Isotopes
c)Isoelectrons atoms
d)None of the above
39.How many electrons in a Hydrogen (H) atom:
a)One
b)Two
c)Three
d)Four
40.The orbital angular momentum of 2p electron is:
a)3h
b)6h
c)Zero         
d)2h/2n

42.The four quantum numbers that could identify the third 3p electron in sulphur are:
a)N = 3, 1 = 0, m = +1, s = +1/2
b)N = 2, 1 = 2, m = -1, s = -1/2
c)N = 3, 1 = 2, m = +1, s = -1/2
d)N = 3, 1 = 1, m = -1, s = +1/2
43.The atomic number of the element with maximum number of unpaired electrons is:
a)23
b)33
c)15
d)26
44.Which of the following orbital is more close to the nucleus?
a)5f
b)6d
c)7s
d)7p
45.The number of d- electrons in F2+ (Z = 26) is not equal to that of:
a)s- electrons in Mg
b)p- electrons in Ne
c)d- electrons in Fe
d)p- electros in CI
 
47.The correct setoff quantum numbers for the unpaired electron of scandium (Z = 21) is:
a)4, 2, 2, +_1/2
b)3, 2, -2, +-1/2           
c)3, 1, 1, +-1/2
d)3, 2, 3, +-1/2


49.The shortest wavelengths of radiation emitted when can electron from infinity falls into the ionized H-atom(RH = 1.097 x 107 m-1)
a)91 nm
b)192 nm
c)406 nm
d)1.9 x 10-8 nm

50.13A27 is a stable isotope. 13AI29 is expected to disintegrate by:
a.emission
b)B- emission
c)Positron emission
d)Proton emission

51.n/p ratio of an element with atomic number greater tha 83 falls in the zone of instability. The element will undergo:
a)a-decay
b)B-decay
c)B+ -decay
d)No decay

52.Proton bombardment of Th230 followed by emission of two alpha particles produces:
a)Rn232
b)Fr223
c)Ra223
d)Fr222

53.In the radioactive decay:
ZAA ___Z-2BA-4___Z-1C-4____ZAA-4
The sequence of radiation emitted is:
a)a, B, y
b)a, B B
c)B, a, a
d)a, y, y

54.Which of the following nuclides  is least likely to be stable?
a)20C40
b)13AI30
c)50Sn119
d)25Mn55

ANSWERS:
1.(c)
2.(c)
3.(c)
5.(a)
6.(c)
7.(c)
8.(b)
9.(a)
10.(c)
11.(c)
12.(c)
13.(b)
14.(b)
15.(b)
16.(d)
17.(a)
18.(d)
19.(b)
20.(d)
21.(c)
22.(b)
23.(b)
24.(c)
25.(a)
26.(b)
27.(a)
28.(d)
29.(c)
30.(b)
31.(b)
32.(b)
33.(c)
34.(a)
35.(c)
36.(a)
37.(b)
38.(b)
39.(a)
40.(d)
42.(d)
43.(d)
44.(c)
45.(d)
47.(b)
49.(a)
50.(b)
51.(a)
52.(b)
53.(b)
54.(b)
 


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