DPP - 1
FEEL
THE
HEAT
Topic : Atomic Structure
Maximum Marks : 40
Subtopic : Bohr’s Atomic Models
Time : 20 min
1. An α - particle with initial speed v0 is 6. The difference in angular momentum
projected from infinity and it approaches up associated with the e– in two successive
to r0 distance from a nuclei. Then, the initial orbits of atom is :-
speed of α - particle, which approaches up to (A)
h
(B)
h
π 2π
2r0 distance from the nucleus, is h h
v0 (C) (D) ( n-1 ) Z
(A) √2 v0 (B) 2
√2
v0
(C) 2 v0 (D) 2
7. The radius of second stationary orbit in
Bohr’s atom is R. The radius of 3rd orbit will
2. If 120 particles are deflected at an angle of be :-
60o , then number of deflected particles at an R
(A) 9R (B) 4
angle of 90o will be : 9R
(A) 30 (B) 60 (C) 4
(D) 2R
(C) 90 (D) 15
8. If the mass of electron is doubled, the radius
3. The ratio of velocity of the electron in the of first orbit of H-atom become about
third and fifth orbit of Li2+ would be : (A) 0.529 Å (B) 0.265 Å
(A) 3:5 (B) 5:3 (C) 1.058 Å (D) 0.32 Å
(C) 25 : 9 (D) 9 : 25
9. The average atomic mass of an element Y is
4. Energy of electron in first orbit of H = – x 41.8. If it exist in form of two isotopes 40Y
eV, then, what would be second ionisation and 42Y, then their percentage of
energy of He? occurrence in the nature is
(A) – 4x (B) 4x (A) 80% ; 20% (B) 10% ; 90%
(C) 2x (D) – 2x (C) 20% ; 80% (D) 90% ; 10%
5. According to Bohr’s theory the approximate 10. Two spherical nuclei have mass numbers
quantum number of a circular orbit of 216 and 64 with their radii R1 and R2
diameter 20.6 nm of the hydrogen atom is :- R
respectively. The ratio �R1 � will be
2
(A) 10 (B) 14
(A) 1.0 (B) 1.5
(C) 12 (D) 16
(C) 2.0 (D) 2.5
