**1)** A negative value for the packing fraction shows that the isotope is

**a)** Unstable

**b)** Very stable

**c)** Artificial

**d)** Stable

**2)** The packing fraction may be

**a)** Positive

**b)** Negative

**c)** Zero

**d)** All the above

**3)** Which does not take place by disintegration?

**a)**

**b)**

**c)**

**d)**

**4)** By removing one -particle from a radioactive isotope, the atomic number

**a)** Increases by one

**b)** Decreases by one

**c)** No change

**d)** Decreases by two

**5)** An isotone of _{32}Ge^{76} is

**a)**

**b)**

**c)**

**d)**

**6)** Bismuth is the end product of the radioactive disintegration series

**a)** 4n

**b)** 4n+l

**c)** 4n+2

**d)** 4n+3

**7)** An isobar of ^{40}_{20}Ca is

**a)**

**b)**

**c)**

**d)**

**8)** A radioisotope has a half-life of 10 years. What percentage of the original amount of it would you expect to remain after 20 years?

**a)** 0

**b)** 12.5

**c)** 25

**d)** 8

**9)** The thorium series starts from Th-232 and ends at

**a)** Pb-208

**b)** Bi-209

**c)** Pb-206

**d)** Pb-207

**10)** With the passage of time, radioactive disintegration

**a)** Increases

**b)** Decreases

**c)** Remains same

**d)** May increase or decrease

**11)** The most radioactive element is

**a)** Uranium

**b)** Thorium

**c)** Radium

**d)** Polonium

**12)** The loss of an -particle is equivalent to the

**a)** Loss of two neutrons

**b)** Loss of two protons

**c)** Loss of two neutrons and two protons

**d)** None of these

**13)** The loss of a -particle is equivalent to the

**a)** Increase of one proton

**b)** Decrease in one neutron

**c)** Combination of both (a) and (b)

**d)** None of these

**14)** How many a-particles are emitted in the nuclear transformation

^{215}_{84}Po^{211}_{82}Pb?

**a)** One

**b)** Two

**c)** Three

**d)** Four

**15)** Of the following radiations, the one most easily stopped by air is

**a)** X-rays

**b)**

**c)**

**d)** Ultra violet rays

**16)** @ The packing fraction is related to the

**a)** Mass defect

**b)** Atomic number

**c)** Nuclear spin

**d)** None

**17)** The total energy given out during the binding up of nucleons in the nucleus is called the

**a)** Nuclear energy

**b)** Binding energy

**c)** Packing fraction

**d)** Fusion energy

**18)** An atom of radium combines with two atoms of chlorine to form RaCl_{2} molecule. The radioactivity of RaCl_{2} will be

**a)** Zero

**b)** One half of the same quantity of Ra

**c)** One third of the same quantity of Ra

**d)** As much as that of the same quantity of Ra

**19)** Which of the following nuclear reactions is correct?

**a)**

**b)**

**c)**

**d)**

**20)** The disintegration constant of a radioactive element is 1.7 x 10^{-6} per sec. Its half-life will be

**a)** 5 days

**b)** 5 hours

**c)** 5 months

**d)** 5 years

**21)** The half-life period of a radioactive nuclide is 3 hours. In 9 hours its activity will be reduced to

**a)** 1/9

**b)** 7/8

**c)** 1/27

**d)** 1/6

**22)** If 12 g of a sample is taken, then 6 g of a sample decays in one hour. The amount of sample showing decay in the next hour is

**a)** 6 g.

**b)** 12 g.

**c)** 3 g.

**d)** 1 g.

**23)** Which of the following are isotonic?

**a)**

**b)**

**c)**

**d)**

**24)** A sample of a radioactive element with t_{1/2} of 11.2 years weighs 2.0 g. After 33.6 years how much is left?

**a)** 0.25 g

**b)** 0.5 g.

**c)** 0.75 g.

**d)** 1.0 g.

**25)** The emission of a beta particle by an atom of an element results in the formation of an

**a)** Isotope

**b)** Isomer

**c)** Isomorph

**d)** Isobar

**26)** The age of rocks on earth or the samples of rocks and dust brought back from the moon can be found by determining the proportion of radioactive … in the rock or dust

**a)** Potassium and stable calcium

**b)** Uranium and stable lead

**c)** Carbon and stable carbon

**d)** Radium and stable lead

**27)** Which is different in isotopes of an element?

**a)** Atomic number

**b)** Mass number

**c)** Number of protons

**d)** Number of electrons

**28)** The reaction ^{27}_{13}Al+ ^{4}_{2}He ^{30}_{14}Si+ ^{1}_{1}H is of the type called

**a)** Nuclear fusion

**b)** Nuclear fission

**c)** Chemical

**d)** Transmutation

**29)** When ^{7}_{3}Li is bombarded with protons, – rays are produced. The nuclide formed is

**a)**

**b)**

**c)**

**d)**

**30)** A certain radioactive isotope has a half-life of 50 days. The fraction of the material left behind after 100 days will be

**a)** 50%

**b)** 75%

**c)** 125%

**d)** 25%

**31)** ^{14}_{6}C in the upper atmosphere is formed by the action of neutrons on

**a)**

**b)**

**c)**

**d)**

**32)** Atoms with the same mass number but having different nuclear charges are called

**a)** Isotopes

**b)** Isobars

**c)** Isochores

**d)** Isotones

**33)** One Curie of activity is equivalent to

**a)**

**b)**

**c)**

**d)** None

**34)** When a radioactive substance is subjected to a vacuum, the rate of disintegration per second

**a)** Increases considerably

**b)** Increases only if the products are gaseous

**c)** Is not affected

**d)** Suffers a slight decrease

**35)** In – decay, the

**a)** N/P decreases

**b)** N/P increases

**c)** N/P remains constant

**d)** None

**36)** The half-life of a radioactive isotope is 1.5 hours. The mass of it that remains undecayed after 6 hours is (the initial mass of the isotope is 32 g)

**a)** 32g

**b)** 16g

**c)** 8g

**d)** 2g

**37)** -rays given off by a radioactive element are from the

**a)** Nucleus

**b)** Valency electrons

**c)** Outer orbit

**d)** All the orbits

**38)** The half-life period of a substance is 1600 minutes. What fraction of the substance will remain after 6400 minutes?

**a)** 1/16

**b)** 1/4

**c)** 1/8

**d)** 1/2

**39)** ^{238}_{92}U is an isotope of uranium. The number of neutrons it can contain is

**a)** 156

**b)** 126

**c)** 146

**d)** 136

**40)** A radioactive element has a half-life of 4.5 x 10^{9} years. If 80 g of this was taken, the time taken for it to decay to 40 g will be

**a)**

**b)**

**c)**

**d)**

**41)** If 8.0 g. of radioactive isotope has a half-life of 10 hours, the half-life of 2.0 g. of the same substance is

**a)** 2.5 hours

**b)** 5.0 hours

**c)** 10 hours

**d)** 40 hours

**42)** A substance is kept for 2 hours, and three fourth of it disintegrates during this period. The half-life of the substance is

**a)** 2 hours

**b)** 1 hour

**c)** 30 minutes

**d)** 2 hours

**43)** 16 g of a radioactive isotope is reduced to 1.0g after one hour. The half-life period of the substance is

**a)** 15 minutes

**b)** 30 minutes

**c)** 45 minutes

**d)** None

**44)** Starting from radium, the radioactive disintegration process terminates when the following is obtained:

**a)** Lead

**b)** Radon

**c)** Radium A

**d)** Radium B

**45)** During – decay,

**a)** An atomic electron is ejected

**b)** An electron which is already present within the nucleus is ejected

**c)** A neutron in the nucleus decays emitting an electron

**d)** A part of the bending of the nucleus is converted into an electron

**46)** The order of penetration of three radioactive rays through a metal sheet is

**a)**

**b)**

**c)**

**d)** None

**47)** Two nuclei are not identical but have the same number of nucleons. These are called

**a)** Isotopes

**b)** Isobars

**c)** Isotones

**d)** None

**48)** The half-life of a radioactive nuclide is 10 months. The fraction of the substance left behind after 40 months is

**a)** 1/2

**b)** 1/4

**c)** 1/8

**d)** 1/16

**49)** The reciprocal of the radioactive decay constant is called the

**a)** Half life period

**b)** Whole life period

**c)** Average life period

**d)** None.

**50)** Which of the following statements is false?

**a)** The atom has a tiny, dense centre or core called nucleus.

**b)** Most of the volume of the atom is empty space

**c)** The nucleus has a small negative electrical charge.

**d)** The electrons revolve around the nucleus.

**51)** Radium has an atomic weight 226 and a half-life of 1600 years. The number of disintegration produced per sec from one g are

**a)** ^{}

**b)**

**c)**

**d)**

**52)** In radioactive decay an emitted electron comes from

**a)** The nucleus of the atom

**b)** The orbit with principal quantum number

**c)** The inner orbital of the atom

**d)** The outermost orbit of the atom

**53)** Which of the following has a magic number of neutrons?

**a)**

**b)**

**c)**

**d)**

**54)** The atomic number of bromine is 35 and its mass number is 80. Two isotopes of bromine are present in equal amounts. Which of the following statement represents the correct number of neutrons in the first and second isotope respectively?

**a)** 34, 36

**b)** 44, 46

**c)** 45, 47

**d)** 79, 81

**55)** In nuclear reactors control rods are used to

**a)** Increase the rate of reaction.

**b)** Decrease the rate of reaction.

**c)** Increase or decrease the rate of reaction .

**d)** Control the temperature

**56)** What is enriched uranium?

**a)** U-238

**b)** U-235

**c)** U-235 + Radium

**d)** U-235 + U-238

**57)** For a nuclear fusion reaction to occur, the temperature required is of the order of

**a)**

**b)**

**c)**

**d)**

**58)** Magic number elements are those isotopes of elements which

**a)** have the number of protons or neutrons as 2, 8, 20, 28, 50, 82, or 126.

**b)** Are relatively more abundant.

**c)** Are unusually stable.

**d)** All of these

**59)** has n/p ratio too low for stability. Its stability can be increased by

**a)** Positron emission

**b)** Beta – decay

**c)** Alpha – decay

**d)** Electron capture

**60)** The projectile experiencing the minimum repulsion on approaching a nucleus is a

**a)**

**b)** Proton

**c)** Neutron

**d)** Positron

**61)** Lead containers are generally used to store radioactive materials, because

**a)** Pb is stable

**b)** Pb has high atomic mass

**c)** Pb is poor conductor

**d)** Pb is a good absorber

**62)** The half-life is 20 days. After 40 days, the amount left is

**a)** 1/2

**b)** 1/4

**c)** 1/8

**d)** 1/16

**63)** A radioactive nuclide dissociates into 1/16th of the initial amount in 2 hours. Its half-life is

**a)** 1 hour

**b)** 30 minutes

**c)** 15 minutes

**d)** 45 minutes

**64)** A radioactive element has a half-life of one day. After three days the amount of the element left will be

**a)** 1/2 of the original

**b)** 1/4 of the original

**c)** 1/8 of the original

**d)** 1/16 of the original

**65)** The missing particle in the reaction + — is a

**a)** Deutron

**b)** Proton

**c)** Neutron

**d)**

**66)** If 75% of a first order reaction is completed in 32 minutes, then 50% of the reaction would be completed in?

**a)** 24 Minutes

**b)** 16 Minutes

**c)** 8 Minutes

**d)** 4 Minutes

**67)** The half life of ^{226}Ra is 1620 years. The time taken to convert 10 g of radium to1.25 g is

**a)** 810 years

**b)** 1620 years

**c)** 3240 years

**d)** 4860 years

**68)** A radioactive substance has a half-life of 5 days. After 20 days it was found that 3 g of the isotope was left in the container. The initial weight of the isotope was

**a)** 48g

**b)** 36g

**c)** 18 g

**d)** 24 g

**69)** 3/4 of a radioactive material decays in 2.5 days. How long will it take for 15/16th of the material to decay?

**a)** 2 days

**b)** 5 days

**c)** 7.5 days

**d)** 10 days

**70)** If the amount of radioactive substance is increased three times, the number of disintegrating atoms per unit time will

**a)** Be doubled

**b)** Triple

**c)** Be one third

**d)** Be unchanged

**71)** The end product of the (4n+2) radioactive disintegration series is

**a)**

**b)**

**c)**

**d)**

**72)** The radioactive isotope which is used to estimate the age of ancient geological formations is

**a)**

**b)**

**c)**

**d)**

**73)** In the following radioactive decay, , how many are ejected from X to form Y?

**a)**

**b)**

**c)**

**d)**

**74)** The symbol X in the following equation is:

**a)** A neutron

**b)** A deutron

**c)** A position

**d)**

**75)** Which element is the end product of every natural radioactive series?

**a)** Pb

**b)** Sn

**c)** C

**d)** Bi

**76)** In radioactive decay, which one of the following moves the fastest?

**a)**

**b)**

**c)**

**d)** Positron

**77)** Which one of the following notations shows the product incorrectly ?

**a)**

**b)** ^{}

**c)**

**d)**

**78)** Which is not emitted by a radioactive substance?

**a)**

**b)**

**c)** Positron

**d)** Proton

**79)** A radioactive element X emits and forms. The element X is

**a)**

**b)**

**c)**

**d)**

**80)** Which of the following is used as a control rod?

**a)** Cadmium rod

**b)** Graphite rod

**c)** Boron

**d)** Both (a) and (c)

**81)** After emission of one alpha and one particle from the number of neutrons in the atom will be

**a)** 142

**b)** 140

**c)** 144

**d)** 143

**82)** @ 1 g of a radioactive element reduces to 125 mg. after 24 hours. The half-life of the isotope is —-?

**a)** 8 hours

**b)** 24 hours

**c)** 6 hours

**d)** 4 hours

**83)** In the reaction , the x is a

**a)** Proton

**b)** Positron

**c)** Electron

**d)** Neutron

**84)** In nuclear reactors, the speed of the neutron is slowed down by

**a)** Heavy water

**b)** Ordinary water

**c)** Zinc rod

**d)** Molten caustic potash.

**85)** In the reaction represented by the sequence, the decays in the sequence are:

**a)**

**b)**

**c)**

**d)** ^{+}

**86)** Of the three isotopes of hydrogen and .,

**a)** All are stable

**b)** Two are unstable

**c)**

**d)**

**87)** The radiation which can penetrate through a 20-cm thick steel plate is

**a)**

**b)**

**c)**

**d)** Positive rays

**88)** In the sun the source of energy is

**a)** Fusion of heavy nuclei

**b)** Fission of heavy nuclei

**c)** Fusion of hydrogen atom

**d)** Fission of uranium atom

**89)** Thermal neutrons have energy of the order of

**a)** 1 Mev

**b)** 1 eV

**c)** 2 eV

**d)** 100 eV

**90)** The huge amount of energy, which is released during atomic fission, is due to the

**a)** Loss of mass

**b)** Loss of proton

**c)**

**d)** Loss of electrons

**91)** In nuclear reactors heavy water is used as a

**a)** Fuel

**b)** Projectile

**c)** Moderator

**d)** Arestor

**92)** The half-life of radioactive radon is 3.8 days. The time at the end of which 1/20th of the radon sample will remain undecayed is about

**a)** 1.6 days

**b)** 16.4 days

**c)** 20 days

**d)** 3.8 x 20 years

**93)** A radioactive element has a t_{1/2} of 60 minutes. The amount left after 3 hours is :

**a)** 17.5%

**b)** 12.5%

**c)** 25%

**d)** 50%

**94)** @ The ratio of the radius of the atom to the nucleus is

**a)**

**b)**

**c)**

**d)**

**95)** A certain nuclide has a half-life of 30 minutes. If one starts with 48 g of it, the amount left at the end of 30 minutes will be

**a)** 24 g

**b)** 16 g

**c)** 8 g

**d)** 6 g

**96)** The binding energy of an element is 64 MeV. If the binding energy per nucleon is 6.4, the number of nucleons is

**a)** 64

**b)** 6

**c)** 10

**d)** 16

**97)** A radioactive isotope having a half-life of three days was received after 12 days. It was found that there was 3 g left in the container. The initial weight of the isotope when packed was

**a)** 12 g

**b)** 24 g

**c)** 36 g

**d)** 48 g

**98)** A sample of radioactive isotope with a half-life of 20 days weighs 1.0 g. After 40 days, the weight of the remaining element is

**a)** 0.5 g

**b)** Zero

**c)** 0.25 g

**d)** 1/6 g

**99)** If 2.0 g of an isotope has a half-life of 20 days, the half-life of 2.3 g of the same sample is

**a)** 20 days

**b)** 10 days

**c)** 40 days

**d)** 5 days

**100)** If 5.0 g. of a radioactive substance has t_{1/2} =14 hours, 20 g. of the same sample will have a t_{1/2 }of

**a)** 56 hr

**b)** 3.5 hr

**c)** 14 hr

**d)** 28 hr

Answer