Atomic Structure — DPP 1

20 NEET questions from Atomic Structure, with answers and explanations. Attempt it as a timed test to get scoring, accuracy breakdown and mistake tracking.

Attempt this test free 20 questions · 30 minutes · +80 marks
1
Species which are isoelectronic to one another are
(a) $\mathrm { CN } ^ { - }$
(b) $\mathrm { OH } ^ { - }$
(c) $\mathrm { CH } _ { 3 } ^ { + }$
(d) $\mathrm { N } _ { 2 }$
(e) CO
Correct answer is
  1. A a, b, c
  2. B a, c, d
  3. C a, d, e
  4. D b, c, d
Show answer & explanation

Correct answer: C

CN¯ → 6 + 8 = 14e¯ ✓
OH¯ → 8 + 2 = 10e¯
CH$_{3}$$^{+}$ → 6 + 2 = 8e¯
N₂ → 7 + 7 = 14e¯ ✓
CO → 6 + 8 = 14e¯ ✓
2
Atomic Structure – NEET-6365 Match the above correct terms:-
  1. A [(i), - a], [(ii) - d], [(iii) - b], [(iv) - c], [(v) - a]
  2. B [(i) - a] [(ii) - d], [(iii) - d] [(iv) - c] [v - a]
  3. C [v -a] [(iv) - c]. [(iii) - d] [(ii) - b] [(i) - a]
  4. D None of them
Show answer & explanation

Correct answer: A

(i) same Z → Isotopes
(ii) same A (p+n) → Isobars
(iii) same n → Isotones
(iv) same n – p → Isodiaphers
(v) same Z → Isotopes.
3
The radius of a shell for H -atom is $4.761 \AA$. The value of $n$ is :-
  1. A 3
  2. B 9
  3. C 5
  4. D 4
Show answer & explanation

Correct answer: A

$\begin{array}{l}\mathrm{r}=0.529 \times \frac{\mathrm{n}^{2}}{\mathrm{Z}} \mathrm{A}^{\circ} \\ \mathrm{n}^{2}=\frac{4.761 \times 1}{0.529}=9 \\ \mathrm{n}=3\end{array}$
4
Multiplication of electron velocity and radius for a orbit in an atom is :-
  1. A Proportional to mass of electron
  2. B Proportional to square of mass of electron
  3. C Inversely proportional to mass of electron
  4. D Does not depend upon mass of electron
Show answer & explanation

Correct answer: C

$\mathrm{mvr}=\frac{\mathrm{nh}}{2 \pi}$
$\mathrm{vr}=\frac{\mathrm{nh}}{2 \pi \mathrm{~m}}$
$\mathrm{vr} \propto \frac{1}{\mathrm{~m}}$
5
For $\mathrm { Li } ^ { + 2 }$ ion, $\mathrm { r } _ { 2 } : \mathrm { r } _ { 5 }$ will be :-
  1. A $9 : 25$
  2. B $4 : 25$
  3. C $25 : 4$
  4. D $25 : 9$
Show answer & explanation

Correct answer: B

r$_{2}$: r$_{5}$
0.529 × $\frac{(2)^{2}}{3}$: & 0.529 × $\frac{(5)^{2}}{3}$
4 : 25
6
The value of planck's constant is $6.63 \times 10 ^ { - 34 }$ Js. The velocity of light is $3.0 \times 10 ^ { 8 } \mathrm {~m} \mathrm {~s} ^ { - 1 }$. Which value is closest to the wavelength in metres of a quantum of light with frequency of $8 \times 10 ^ { 15 } \mathrm {~s} ^ { - 1 }$ ?
  1. A $3 \times 10 ^ { 7 }$
  2. B $2 \times 10 ^ { - 25 }$
  3. C $5 \times 10 ^ { - 18 }$
  4. D $3.75 \times 10 ^ { - 8 }$
Show answer & explanation

Correct answer: D

$v=\frac{c}{\lambda} \Rightarrow \lambda=\frac{c}{v}=\frac{3 \times 10^{8}}{8 \times 10^{15}}$
= 0.375 × 10$^{-7}$m
= 3.75 × 10$^{-8}$m
7
Angular momentum in second Bohr orbit of H -atom is x . Then find out angular momentum in $\mathrm { I } ^ { \text {st } }$ excited state of $\mathrm { Li } ^ { + 2 }$ ion :
  1. A 3x
  2. B 9x
  3. C $\frac { x } { 2 }$
  4. D x
Show answer & explanation

Correct answer: D

mvr = $\frac{2 \mathrm{~h}}{2 \pi}$ = x (given) [for H–atom]

mvr = $\frac{2 \mathrm{~h}}{2 \pi}$ = [for Ist exited state of Li$^{+2}$ Ion]

mvr = x
8
The relative abundance of two rubidium isotopes of atomic weights 85 and 87 are $75 \%$ and $25 \%$ respectively. The average atomic weight of rubidium is:-
  1. A 75.5
  2. B 85.5
  3. C 86.5
  4. D 87.5
Show answer & explanation

Correct answer: B

Average Atomic weight
$=\frac{85 \times 75+87 \times 25}{75+25}$

$=\frac{6375+2175}{100}=\frac{8550}{100}$

= 85.5
9
In Bohr's atomic model radius of $\mathrm { I } ^ { \text {st } }$ orbit of Hydrogen is 0.053 nm then radius of $3 ^ { \text {rd } }$ orbit of $\mathrm { Li } ^ { + 2 }$ is :
  1. A 0.159 nm
  2. B 0.053 nm
  3. C 0.023 nm
  4. D 0.026 nm
Show answer & explanation

Correct answer: A

r$_{H}$ = 0.053 nm = 0.053 × $\frac{(1)^{2}}{1}$
$\mathrm{r}_{\mathrm{Li}^{+z}}$ = 0.053 × $\frac{(3)^{2}}{3}$
$\mathrm{r}_{\mathrm{Li}^{+z}}$ = 0.0159 nm
10
The $\mathrm { e } / \mathrm { m }$ ratio is maximum for :-
  1. A $\mathrm { D } ^ { + }$
  2. B $\mathrm { He } ^ { + }$
  3. C $\mathrm { H } ^ { + }$
  4. D $\mathrm { He } ^ { 2 + }$
Show answer & explanation

Correct answer: C

Atomic Structure – NEET-6373 Maximum e/m ration is of H$^{+}$.

11
An isotone of ${ } _ { 32 } ^ { 76 } \mathrm { Ge }$ is :-
(i) ${ } _ { 32 } ^ { 77 } \mathrm { Ge }$

(ii) ${ } _ { 33 } ^ { 77 } \mathrm { As }$

(iii) ${ } _ { 34 } ^ { 77 } \mathrm { Se }$

(iv) ${ } _ { 34 } ^ { 78 } \mathrm { Se }$
  1. A (ii) & (iii)
  2. B (i) & (ii)
  3. C (ii) & (iv)
  4. D (ii) & (iii) & (iv)
Show answer & explanation

Correct answer: C

Same number of (n–p) ⇒ Isotones
${ }_{32}^{77} \mathrm{Ge}$ ⇒ 76 – 32 = 44 = no. of n
no. of n of ${ }_{33}^{77} \mathrm{As}$ ⇒ 77 – 33 = 44
no. of n of ${ }_{34}^{78} \mathrm{Se}$ ⇒ 78 – 34 = 44
12
Number of protons, neutrons & electrons in the element ${ } _ { 89 } ^ { 231 } \gamma$ is :-
  1. A $89,231,89$
  2. B $89,89,242$
  3. C $89,142,89$
  4. D $89,71,89$
Show answer & explanation

Correct answer: C

Atomic Structure – NEET-6371

13
Atomic weight of Ne is 20.2 . Ne is mixture of ${ } ^ { 20 } \mathrm { Ne }$ and ${ } ^ { 22 } \mathrm { Ne }$, relative abundance of heavier isotope is :-
  1. A 90
  2. B 20
  3. C 40
  4. D 10
Show answer & explanation

Correct answer: D

Let Percentage of $^{20}$Ne = x%
$^{22}$Ne = 100 – x %
Average atomic weight ⇒ 20.2
= $\frac{(20 \times x)+22(100-x)}{100}$
2x = 180
x = 90
$^{20}$Ne = 90%
$^{22}$Ne = 10% → heavier Isotope.
14
Atoms ${ } _ { 6 } ^ { 13 } \mathrm { C }$ and ${ } _ { 8 } ^ { 17 } \mathrm { O }$ are related to each other as:-
  1. A Isotones
  2. B Isoelectronic
  3. C Isodiaphers
  4. D Isosters
Show answer & explanation

Correct answer: C

${ }_{6}^{13}$ → 7 – 6 = 1
${ }_{8}^{17}$ → 9 – 8 = 1
Same (n – p) Isodiaphers
15
Which of the following pairs is correctly matched:
  1. A Isotopes - ${ } _ { 20 } ^ { 40 } \mathrm { Ca } , { } _ { 19 } ^ { 40 } \mathrm {~K}$
  2. B Isotones - ${ } _ { 14 } ^ { 30 } \mathrm { Si } , { } _ { 15 } ^ { 31 } \mathrm { P } , { } _ { 16 } ^ { 32 } \mathrm {~S}$
  3. C Isobars - ${ } _ { 8 } ^ { 16 } \mathrm { O } , { } _ { 8 } ^ { 17 } \mathrm { O } , { } _ { 8 } ^ { 18 } \mathrm { O }$
  4. D Isoelectronic - $\mathrm { N } ^ { - 3 } , \mathrm { O } ^ { - 2 } , \mathrm { Cr } ^ { + 3 }$
Show answer & explanation

Correct answer: B

Isotones → n same
${ }_{14}^{30} \mathrm{Si}$ ⇒ 30 – 14 = 16
${ }_{15}^{31} \mathrm{P}$ ⇒ 31 – 15 = 16
${ }_{16}^{32} \mathrm{~S}$ ⇒ 32 – 16 = 16
16
The ratio of specific charge of a proton and an $\alpha$-particle is :-
  1. A $2 : 1$
  2. B $1 : 2$
  3. C $1 : 4$
  4. D $1 : 1$
Show answer & explanation

Correct answer: A

$\begin{array}{l}\text { Specific charge }=\frac{\text { Charge }(\mathrm{e})}{\text { mass }(\mathrm{m})} \\ \frac{\text { S.C. }_{\mathrm{p}}}{\text { S.C. }_{\alpha}}=\frac{\mathrm{e}_{\mathrm{p}} / \mathrm{m}_{\mathrm{p}}}{\mathrm{e}_{\alpha} / \mathrm{m}_{\alpha}}=\frac{1 / 1}{2 / 4}=\frac{2}{1}\end{array}$
17
Choose the false statement about deuterium:-
  1. A It is an isotope of hydrogen
  2. B It contains [(1e) + (1p) + (1n)]
  3. C It contains only [(1p) + (1n)]
  4. D D$_{2}$O is called as heavy water
Show answer & explanation

Correct answer: C

Deuterium $_{1 }$H$^{2}$
p → 1
e → 1
n → 1
18
Find out the atoms which are isoneutronic :-
  1. A ${ }_{6}^{14} \mathrm{C},{ }_{7}^{15} \mathrm{~N},{ }_{9}^{17} \mathrm{~F}$
  2. B ${ }_{6}^{12} \mathrm{C},{ }_{7}^{14} \mathrm{~N},{ }_{9}^{19} \mathrm{~F}$
  3. C ${ }_{6}^{14} \mathrm{C},{ }_{7}^{14} \mathrm{~N},{ }_{9}^{17} \mathrm{~F}$
  4. D ${ }_{6}^{14} \mathrm{C},{ }_{7}^{14} \mathrm{~N},{ }_{9}^{19} \mathrm{~F}$
Show answer & explanation

Correct answer: A

Atomic Structure – NEET-6357
19
The radius ratio of first three Bohr orbits is :-
  1. A $1 : 0. 5 : 0.5$
  2. B $1 : 2 : 3$
  3. C $1 : 4 : 9$
  4. D $1 : 8 : 27$
Show answer & explanation

Correct answer: C

Atomic Structure – NEET-6382
20
In ${ } _ { 7 } ^ { 14 } \mathrm {~N}$ if mass attributed to electrons were doubled & the mass attributed to protons were halved, the atomic mass would become approximately :-
  1. A Halved
  2. B Doubled
  3. C Reduced by $25 \%$
  4. D Remain same
Show answer & explanation

Correct answer: C

Atomic Structure – NEET-6375 % change = $\frac{3.5}{14}$ × 100 = 25% Reduces.

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