NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev

Physics Class 12

NEET : NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev

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Q.1. For which one of the following, Bohr model is not valid?     (2020)
(a) Deuteron atom
(b) Singly ionised neon atom (Ne+)
(c) Hydrogen atom
(d) Singly ionised helium atom (He+)
Ans:
b

Bohr Model is valid only for those atoms which have one electron in orbit.

NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRevBohr Model

Q.2. The total energy of an electron in an atom in an orbit is –3.4 eV. Its kinetic and potential energies are, respectively:    (2019)
(a) –3.4 eV, –3.4 eV
(b) –3.4 eV, –6.8 eV
(c) 3.4 eV, –6.8 eV
(d) 3.4 eV, 3.4 eV
Ans
: c

In Bohr's model of H atom
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev
∴ K.E. = 3.4 eV
U = –6.8 eV

Q.3. α-particle consists of :    (2019)
(a) 2 protons and 2 neutrons only
(b) 2 electrons, 2 protons and 2 neutrons
(c) 2 electrons and 4 protons only
(d) 2 protons only
Ans:
a

α-particle is nucleus of Helium which has two protons and two neutrons.

Q.4. The ratio of kinetic energy to the total energy of an electron in a Bohr orbit of the hydrogen atom,is :-    (2018)
(a) 1 : 1
(b) 1 : –1
(c) 2 : –1
(d) 1 : –2
Ans: 
b

NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev

Q.5. Suppose the charge of a proton and an electron differ slightly. One of them is – e, the other is(e + De). If the net of electrostatic force and gravitational force between two hydrogen atoms placed at a distance d (much greater than atomic size) apart is zero, then De is of the order of [Given mass of hydrogen mh = 1.67 × 10–27 kg]     (2017)
(a) 10–23 C
(b) 10–37 C
(c) 10–47 C
(d) 10–20 C
Ans: 
b

We know, a hydrogen atom has one electron and one proton
so, net charge on each hydrogen atom = (e + ∆e - e) = ∆e
so, electrostatic force , NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev
gravitational force, NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev
where Mh denotes mass of hydrogen
a/c to question,
gravitational force = electrostatic force
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev
we know, K = 9 × 109 Nm²/C², G = 6.67 × 10-11 Nm²/Kg² , Mh = 1.67 × 10-27 Kg
so, 9 × 109 × ∆e² = 6.67 × 10-11 × (1.67 × 10-27)²
or, ∆e² = 6.67 × 10-11 × 1.67 × 1.67 × 10-54/9 × 109
or, ∆e = 1.43767 × 10-37 C

Q.6. The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is :-     (2017)
(a) 1
(b) 4
(c) 0.5
(d) 2
Ans: 
b

For last line of Balmer : n1 = 2 & n2 = ∞
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev
For last line Lyman series : n1 = 1 & n2 = ∞
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev

Q.7. When an α-particle of mass 'm' moving with velocity 'v' bombards on a heavy nucleus of charge 'Ze' its distance of closet approach from the nucleus depends on m as :    (2016)
(a) m
(b) 1/m
(c) 1/√m
(d) 1/m2
Ans:
b

When an alpha particle moving with velocity v bombards on a heavy nucleus of charge Ze, then there will be no loss of energy.
Initial Kinetic energy of the alpha particle = Potential energy of alpha particle at closest approach.
That is,
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev
This is the required distance of closest approach to alpha particle from the nucleus.
When an alpha particle moving with velocity v bombards on a heavy nucleus of charge Ze, then there will be no loss of energy.
Initial Kinetic energy of the alpha particle = Potential energy of alpha particle at closest approach.
That is,
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev
This is the required distance of closest approach to alpha particle from the nucleus.

Q.8. Given the value of Rydberg constant is 107 m-1, the wave number of the last line of the Balmer series in hydrogen spectrum will be :     (2016)
(a) 2.5 x 107m-1
(b) 0.025 x 104m-1
(c) 0.5 x 107m-1
(d) 0.25 x 107m-1
Ans: 
d

Rydberg constant, r = 107 m-1
For last line in Balmer series,
n2 = ∞; n1 = 2
We know,
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev

Q.9. Consider 3rd orbit of He+ (Helium), using non-relativistic approach, the speed of electron in this orbit will be [given K = 9 x 109 constant, Z = 2 and h(Planck's Constant) = 6.6 x 10-34 J s]    (2015)
(a) 3.0 x 108 m/s
(b) 2.92 x 106 m/s
(c) 1.46 x 106 m/s
(d) 0.73 x 106 m/s
Ans:
c

NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev

Q.10. If radius of theNEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRevnucleus is taken to be RAl, then the radius ofNEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRevnucleus is nearly :    (2015)

(a)
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev

(b)

NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev

(c)

NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev

(d)

NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev
Ans: 
c

Radius of the nucleus goes as R ∝ A1/3, where A is the atomic mass. If RTe is the radius of the nucleus of telurium atom and RAl is the radius of the nucleus of aluminium atom we have

NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev

Q.11. Hydrogen atom in ground state is excited by a monochromatic radiation of λ = 975 Å. Number of spectral lines in the resulting spectrum emitted will be:     (2014)
(a) 6
(b) 10
(c) 3
(d) 2
Ans: 
a
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev
NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev

NEET Previous Year Questions (2014-20): Atoms NEET Notes | EduRev

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