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Previous Year Questions of Atomic Structure and Radioactivity for NDA

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Previous Year Questions of Atomic Structure and Radioactivity for NDA

Q 2714201150

Rutherford's alpha-particle scattering experiment" was responsibie for the discovery of
NDA Paper 2 2017
(A)

Electron

(B)

Proton

(C)

Nucleus

(D)

Helium

Solution:

Correct Answer is `=>` (C) Nucleus
Q 2179401316

An atom of carbon has `6` protons. Its mass number is `12`.
How many neutrons are present in an atom of carbon ?
NDA Paper 2 2016
(A)

`12`

(B)

`6`

(C)

`10`

(D)

`14`

Solution:

We know that,

Mass no. `(A) =` No. of proton `(p) + `no. of neutron `(n)`

`12 = 6 + n => n = 6`

Mass number determines the atomic mass of atoms.
Correct Answer is `=>` (B) `6`
Q 2272856736

Which one of the following statements is correct?
NDA Paper 2 2015
(A)

Rutherford's alpha-particle scattering experiment led to the discovery of electron

(B)

J J Thomson suggested that the nucleus of an atom contains protons

(C)

The atomic number of an element is the same as the number of protons in the nucleus of its atom

(D)

The mass number of an atom is equal to the number of electrons in its shells

Solution:

Rutherford's a-scattering experiment led to the discovery of nucleus and hence structure of atoms. JJ Thomson's cathode ray tube experiment led to the discovery of electrons. Atomic number of an element is equal to the number of protons in the nucleus of an atom. Mass number of an atom is equal to the sum of total number of neutrons and protons in the nucleus.
Correct Answer is `=>` (C) The atomic number of an element is the same as the number of protons in the nucleus of its atom
Q 1760123015

Which one among the following contains the most neutrons?
NDA Paper 2 2014
(A)

` text()_26^59Fe`

(B)

` text()_29^61Cu`

(C)

` text()_30^61Zn`

(D)

` text()_30^60Zn^(2+)`

Solution:

Number of neutrons in ` text()_26^59Fe = 33`

Number of neutrons in ` text()_29^61Cu = 32`

Number of neutrons in ` text()_30^61Zn = 31`

Number of neutrons in ` text()_30^60Zn^(2+) = 30`
Correct Answer is `=>` (A) ` text()_26^59Fe`
Q 1712556430

Which of the following pairs represents isoelectronic ions?
NDA Paper 2 2014
(A)

`Na^+ ,K^+`

(B)

`K^+,Mg^(2+)`

(C)

`Mg^(2+) , Ca^(2+)`

(D)

`Ca^(2+) , S^(2-)`

Solution:

Number of neutrons in ` text()_26^59Fe = 33`

Number of neutrons in ` text()_29^61Cu = 32`

Number of neutrons in ` text()_30^61Zn = 31`

Number of neutrons in ` text()_30^60Zn^(2+) = 30`
Correct Answer is `=>` (D) `Ca^(2+) , S^(2-)`
Q 1763101945

The mass number of an atom is determined by.
NDA Paper 2 2014
(A)

adding the number for neutrons and number of electrons

(B)

adding the number of protons and number of electrons

(C)

the number of protons only

(D)

adding the number of neutrons and number of protons

Solution:

Number of neutrons in ` text()_26^59Fe = 33`

Number of neutrons in ` text()_29^61Cu = 32`

Number of neutrons in ` text()_30^61Zn = 31`

Number of neutrons in ` text()_30^60Zn^(2+) = 30`
Correct Answer is `=>` (D) adding the number of neutrons and number of protons
Q 1742267133

Which of the following is the correct electronic configuration of chlorine?

NDA Paper 2 2014
(A)

`2, 7, 8`

(B)

`2, 8, 7`

(C)

`2, 8, 8`

(D)

`7, 8, 9`

Solution:

We know that,

atomic number of chlorine `= 17`

so, its electronic configuration `= 2, 8, 7`
Correct Answer is `=>` (B) `2, 8, 7`
Q 1721834721

A monatomic species that has `18` electrons and a net charge of `2-` has
NDA Paper 2 2014
(A)

the same number of electrons as a neutral argon atom

(B)

more protons than electrons

(C)

2 unpaired electrons

(D)

20 protons

Solution:

A monatomic species has the same number

of electrons as a neutral argon atom.
Correct Answer is `=>` (A) the same number of electrons as a neutral argon atom
Q 1753067844

The most of the mass of the atom can be found in
NDA Paper 2 2014
(A)

electrons

(B)

charges

(C)

nucleus

(D)

electron cloud

Solution:

The most of the mass of the atom can be

found in nucleus of atom.
Correct Answer is `=>` (C) nucleus
Q 2366291175

Two atoms are said to be isotopes, if
NDA Paper 2 2013
(A)

they have the same atomic number, but different mass numbers

(B)

they have the same number of neutrons, but different mass numbers

(C)

the sum of the number of protons and neutrons is the same, but the number of protons is different

(D)

they have the same number of neutrons, but different modes of radioactive decay

Solution:

Two atoms are said to be isotopes if they have the same atomic number but different mass numbers.
Correct Answer is `=>` (A) they have the same atomic number, but different mass numbers
Q 2317745680

The phenomenon of radioactivity was discovered by
NDA Paper 2 2013
(A)

Marie Curie

(B)

Pierre Curie

(C)

Henri Becquerel

(D)

J J Thomson

Solution:

Phenomenon of radioactivity was first discovered by Henri Becquerel in 1896. while studying fluorescence and phosphorence of compounds irradiated by visible light.
Correct Answer is `=>` (A) Marie Curie
Q 2317145980

The process of nuclear fusion in the sun requires
NDA Paper 2 2012
(A)

very high temperature and very high pressure

(B)

low temperature and high pressure

(C)

high temperature and low pressure

(D)

very high temperature and no pressure

Solution:

Nuclear fusion is the process by which two or more atomic nuclei join together, or 'fuse', to form a single heavier nucleus. During this process, matter is not conserved because some of the mass of the fusing nuclei is converted to energy which is released. Fusion is the process that powers active stars. The Sun is a main-sequence star, and thus generates its energy by nuclear fusion of hydrogen nuclei into helium.
Correct Answer is `=>` (A) very high temperature and very high pressure
Q 2347145983

Which one among the following transitions is associated with the largest change in energy in hydrogen atom?
NDA Paper 2 2012
(A)

n = 5 to n = 3

(B)

n = 2 to n = 1

(C)

n = 3 to = 2

(D)

n = 4 to = 2

Solution:

`n = 3` to` = 2`

The energies of the different stationary states in case of hydrogen atom are given by

`E_n = - (1312z^2)/(n^2)` z = 1 for n atom

Transition n = 3 to = 2 is associated with the largest change in energy in hydrogen atom.
Correct Answer is `=>` (C) n = 3 to = 2
Q 2387156087

Match the following






Column IColumn II
(A) Goldstein (1) Atomic theory
(B) Chadwick (2) Proton
(C) JJ Thomson (3) Neutron
(D) John Dalton (4) Electron

NDA Paper 2 2012
(A)

2, 3, 4, 1

(B)

2, 4, 3, 1

(C)

1, 4, 3, 2

(D)

1, 3, 4, 2

Solution:

In chemistry and physics, `text(atomic theory)` is a theory of the nature of matter, which states that matter is composed of discrete units called atoms, as opposed to the obsolete notion that matter could be divided into any arbitrarily small quantity. It was discovered by `"John Dalton"`. The `"proton"` is a subatomic particle with the symbol `p` or `p^+` and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom. It was discovered by `"Goldstein"`. The `"neutron"` is a subatomic hadron particle which has the symbol n, no net electric charge and a mass lightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. It was discovered by `"Chadwick"`. An electron has no known components or substructure; in other words, it is generally thought to be an elementary particle. It was discovered by `"JJ Thomson"`.
Correct Answer is `=>` (A) 2, 3, 4, 1
Q 2387856787

The penetrating power of X-rays can be increased by
NDA Paper 2 2012
(A)

increasing the current in the filament

(B)

decreasing the potential difference between the cathode and the anode

(C)

decreasing the current in the filament

(D)

increasing the potential difference between the cathode and the anode

Solution:

The penetrating power of X-rays can be increased by increasing the potential difference between the cathode and the anode.
Correct Answer is `=>` (D) increasing the potential difference between the cathode and the anode
Q 2337167082

Which one among the following transitions of electron of hydrogen atom emits radiation of the shortest wavelength?
NDA Paper 2 2012
(A)

n = 2 to n = 1

(B)

n = 3 to n = 2

(C)

n = 4 to n = 3

(D)

n = 5 to n= 4

Solution:

Rydberg gave a very simple theoretical equation for the calculation of the wavelength of number of lines present in hydrogen spectrum

`overset(ul)(v) = R(1/(n_1^2) - 1/(n_2^2))`
when electrons jumps from n = 2 to n = 1 the hydrogen atom emits radiation of the shortest wavelength.
Correct Answer is `=>` (A) n = 2 to n = 1
Q 2347467383

Which one among the following is correct regarding `text()^20Ne, text()^23 Na^+, text()^19 F^(-) and text()^24Mg^(2+)`?
NDA Paper 2 2012
(A)

They are isomers of each other

(B)

They are isotopes of each other

(C)

They are isoelectronic with each other

(D)

All of the above

Solution:

When two elements and/or ions have the same electronic configuration it is said that they are 'isoelectronic' with one another
`Ne, Na^+, F^-` and `Mg^(2+)` have 10 electrons and have the same electronic configuration `1s^2 2s^2 2p^6`
Correct Answer is `=>` (C) They are isoelectronic with each other
Q 2377467386

Which of the following pairs is/are correctly matched'?
1. Isotopes Atoms with same atomic number but different atomic mass.
2. Isobars Atoms with same number of neutrons but different atomic number.
3. Isotones Atoms with same mass number but different atomic number.
Select the correct answer using the codes given below
NDA Paper 2 2012
(A)

1, 2 and 3

(B)

Only 1

(C)

1 and 2

(D)

Only 2

Solution:

When two elements and/or ions have the same electronic configuration it is said that they are 'isoelectronic' with one another
`Ne, Na^+, F^-` and `Mg^(2+)` have 10 electrons and have the same electronic configuration `1s^2 2s^2 2p^6`
Correct Answer is `=>` (C) 1 and 2
Q 2317567480

The nucleus of a singly ionised carbon atom contains
NDA Paper 2 2012
(A)

6 protons and 6 neutrons

(B)

5 protons and 6 neutrons

(C)

6 protons, 6 neutrons and 6 electrons

(D)

12 protons, 6 neutrons and 6 electrons

Solution:

When two elements and/or ions have the same electronic configuration it is said that they are 'isoelectronic' with one another
`Ne, Na^+, F^-` and `Mg^(2+)` have 10 electrons and have the same electronic configuration `1s^2 2s^2 2p^6`
Correct Answer is `=>` (A) 6 protons and 6 neutrons
Q 2337278182

Which one among the following most correctly determines the atomic number of an element'?
NDA Paper 2 2011
(A)

Number of protons

(B)

Number of protons and electrons

(C)

Number of ions

(D)

Number of nucleons

Solution:

The number of protons present in an atom is known as its atomic number. It is generally denoted by the letter Z. Atomic number is the fundamental property of an element. It is determined by Moseley in 1913. In a neutral atom, it is also equal to the number of electrons.
Atomic number (Z) = Number of protons
= Number of electrons (in neutral atom)
Correct Answer is `=>` (A) Number of protons
Q 2307678588

The number of protons in a negatively charged atom (anion) is
NDA Paper 2 2011
(A)

more than the atomic number of the element

(B)

less than the atomic number of the element

(C)

more than the number of electrons in the atom

(D)

less than the number of electrons in the atom

Solution:

In a neutral atom, number of protons is equal to number of electrons but in a negatively charged atom (anion). the number of protons is less than the number of electrons. An anion is formed by the gain of electron.

`F + e^(-) -> F^-`

Number of p = 9 Number of p = 9
Number of `e^-` = 9 Number of `e^-` = 10
Correct Answer is `=>` (D) less than the number of electrons in the atom
Q 2367778685

A stable nucleus (light with A< 1 0) has
NDA Paper 2 2011
(A)

exactly the same number of neutrons and protons

(B)

more neutrons than protons

(C)

no neutrons

(D)

no protons

Solution:

A stable nucleus has exactly the same number of neutrons and protons. For nuclei having atomic number upto 20, the `N/Z` ratio is close to unity. The maximum stability of nucleus is z attained when `N/Z = 1` or N = Z. (where, N is number of neutrons and Z is the atomic number or number of protons.)
Correct Answer is `=>` (A) exactly the same number of neutrons and protons
Q 2358412304

Which one of the following statements is correct?
NDA Paper 2 2010
(A)

Only electrons reside inside the nucleus of an atom

(B)

Both electrons and protons reside inside the nucleus of an atom

(C)

Only neutrons reside inside the nucleus of an atom

(D)

Both protons and neutrons can reside inside the nucleus of an atom

Solution:

Nucleus contains neutrons and protons. These particles collectively are also referred to as nucleons. Electrons are not present in the nucleus of an atom.
Nucleon = Neutron + Proton
Correct Answer is `=>` (D) Both protons and neutrons can reside inside the nucleus of an atom
Q 2308512408

The number of neutrons in `text()_13 Al^27` is
NDA Paper 2 2010
(A)

40

(B)

27

(C)

14

(D)

13

Solution:

Number of neutrons= Mass number- Atomic number for `text()_13 Al^27`

Atomic number `= 13`
Mass number `= 27`
Number of neutrons =` 27 - 13 = 14`
Correct Answer is `=>` (C) 14
Q 2367834785

Which one among the following is used as a moderator in nuclear reactors?
NDA Paper 2 2009
(A)

Ozone

(B)

Heavy hydrogen

(C)

Heavy water

(D)

Hydrogen peroxide

Solution:

In nuclear reactor, heavy water (`D_2O`) is used to slow down the speed of neutrons, i.e., as moderator. When the fast moving neutrons collide with moderator, they lose energy and get slow down.
Correct Answer is `=>` (C) Heavy water
Q 2327056881

Which of the following statements with regard to isotopes and isobars is/are correct?
l. Isotopes have same mass number.
2. Isobars have same atomic number.
Select the correct answer using the codes given below.
NDA Paper 2 2008
(A)

Only 1

(B)

Only 2

(C)

Both 1 and 2

(D)

Neither 1 nor 2

Solution:

Isotopes have the same atomic number and different
mass number. e.g., `text()_1H^1` , `text()_1H^2, text()_1H^1` are the three isotopes of
hydrogen.

Isobars have the same mass number but different atomic
number. e.g `text()_88Ra^( 228), text()_89Ac^( 228)`
Correct Answer is `=>` (D) Neither 1 nor 2
Q 2377280186

Which one of the following is the correct statement'?
The force binding the nucleons inside the nucleus is
NDA Paper 2 2007
(A)

charge dependent

(B)

strong and highly repulsive

(C)

a central force

(D)

charge independent

Solution:

Nuclear forces between protons and protons, between neutrons and neutrons and between protons and neutrons are all essentially the same in magnitude. Thus, we can say that nuclear forces are charge independent.
Correct Answer is `=>` (D) charge independent
Q 2327780681

The oxide of which of the following elements is used as a coolant'?
NDA Paper 2 2007
(A)

Silicon

(B)

Nitrogen

(C)

Carbon

(D)

Phosphorus

Solution:

Solid carbon dioxide is used as a refrigerant (coolant).
Correct Answer is `=>` (C) Carbon
Q 2317780689

The oxide of which of the following elements is used as a coolant'?
NDA Paper 2 2007
(A)

Silicon

(B)

Nitrogen

(C)

Carbon

(D)

Phosphorus

Solution:

Solid carbon dioxide is used as a refrigerant (coolant).
Correct Answer is `=>` (C) Carbon
 
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