NEET > Atoms and Nuclei

Explore popular questions from Atoms and Nuclei for NEET. This collection covers Atoms and Nuclei previous year NEET questions hand picked by popular teachers.


Q 1.    

Correct4

Incorrect-1

The potential energy associated with an electron in the orbit

A

increases with the increases in radii of the orbit

decreases with the increase in the radii of the orbit

C

remains the same with the change in the radii of the orbit

D

None of these

Explanation

Q 2.    

Correct4

Incorrect-1

The diagram shows the energy levels for an electron in a certain atom. Which transition shown represents the emission of a photon with the most energy?

A

{tex} \mathrm {IV } {/tex}

{tex}\mathrm{III} {/tex}

C

{tex}\mathrm{II}{/tex}

D

{tex}\mathrm{I}{/tex}

Explanation





Q 3.    

Correct4

Incorrect-1

Electrons in a certain energy level {tex} n = n _ { 1 } , {/tex} can emit 3 spectral lines. When they are in another energy level, {tex} n = n _ { 2 } . {/tex} They
can emit 6 spectral lines. The orbital speed of the electrons in the two orbits are in the ratio of

{tex} 4 : 3 {/tex}

B

{tex} 3 : 4 {/tex}

C

{tex} 2 : 1 {/tex}

D

{tex} 1 : 2 {/tex}

Explanation





Q 4.    

Correct4

Incorrect-1

In Ruther ford scattering experiment, the number of {tex} \alpha {/tex} -particles scattered at {tex} 60 ^ { \circ } {/tex} is {tex} 5 \times 10 ^ { 6 } . {/tex} The number of
{tex} \alpha {/tex} -particles scattered at {tex} 120 ^ { \circ } {/tex} will be

A

{tex} 15 \times 10 ^ { 6 } {/tex}

B

{tex} \frac { 3 } { 5 } \times 10 ^ { 6 } {/tex}

{tex} \frac { 5 } { 9 } \times 10 ^ { 6 } {/tex}

D

None of these

Explanation



Q 5.    

Correct4

Incorrect-1

In the Bohr model an electron moves in a circular orbit around the proton. Considering the orbiting electron to be a circular
current loop, the magnetic moment of the hydrogen atom, when the electron is in {tex} n ^ { \text {th } } {/tex} excited state, is :

A

{tex} \left( \frac { e } { 2 m } \frac { n ^ { 2 } h } { 2 \pi } \right) {/tex}

B

{tex} \left( \frac { e } { m } \right) \frac { n h } { 2 \pi } {/tex}

{tex} \left( \frac { e } { 2 m } \right) \frac { n h } { 2 \pi } {/tex}

D

{tex} \left( \frac { e } { m } \right) \frac { n ^ { 2 } h } { 2 \pi } {/tex}

Explanation





Q 6.    

Correct4

Incorrect-1

A 12.5 eV electron beam is used to bombard gaseous hydrogen at room temperature. It will emit:

2 lines in the Lyman series and 1 line in the Balmar series

B

3 lines in the Lyman series

C

1 line in the Lyman series and 2 lines in the Balmar series

D

3 lines in the Balmer series

Explanation







Q 7.    

Correct4

Incorrect-1

A Hydrogen atom and a {tex}\mathrm{Li^{++}}{/tex}ion are both in the second excited state. If {tex} \ell _ { \mathrm { H } } {/tex} and {tex} \ell _ { \mathrm { Li } } {/tex} are their respective electronic
angular momenta, and {tex} E _ { \mathrm { H } } {/tex} and {tex} E _ { \mathrm { Li } } {/tex} their respective energies, then

A

{tex} \ell _ { \mathrm { H } } > \ell _ { \mathrm { Li } } {/tex} and {tex} \left| E _ { \mathrm { H } } \right| > | E _ { \mathrm { Li } }| {/tex}

{tex} \ell _ { \mathrm { H } } = \ell _ { \mathrm { Li } } {/tex} and {tex} \left| E _ { \mathrm { H } } \right| < \left| E _ { \mathrm { Li } } \right| {/tex}

C

{tex} \ell _ { \mathrm { H } } = \ell _ { \mathrm { Li } } {/tex} and {tex} \left| E _ { \mathrm { H } } \right| > \left| E _ { \mathrm { Li } } \right| {/tex}

D

{tex} \ell _ { \mathrm { H } } < \ell _ { \mathrm { Li } } {/tex} and {tex} \left| E _ { \mathrm { H } } \right| < \left| E _ { \mathrm { Li } } \right| {/tex}

Explanation

Q 8.    

Correct4

Incorrect-1

The radius of hydrogen atom in its ground state is {tex} 5.3 \times 10 ^ { - 11 } \mathrm { m } . {/tex} After collision with an electron it is found to
have a radius of {tex} 21.2 \times 10 ^ { - 11 } \mathrm { m } {/tex} . What is the principal quantum number {tex} \mathrm { n } {/tex} of the final state of the atom

A

{tex} n = 4 {/tex}

{tex} n = 2 {/tex}

C

{tex} n = 16 {/tex}

D

{tex} n = 3 {/tex}

Explanation

Q 9.    

Correct4

Incorrect-1

When hydrogen atom is in its first excited level, its radius is

four times its ground state radius

B

twice

C

same

D

half

Explanation

Q 10.    

Correct4

Incorrect-1

Consider {tex} 3 ^ { \text {rd } } {/tex} orbit of {tex} \mathrm { He } ^ { + } {/tex} (Helium), using non-relativistic approach, the speed of electron in this orbit will be {tex} [ \text {given } \mathrm { K } {/tex}
{tex} = 9 \times 10 ^ { 9 } {/tex} constant {tex} , Z = 2 {/tex} and {tex} h {/tex} (Plank's Constant) {tex} \left. = 6.6 \times 10 ^ { - 34 } \mathrm { Js } \right] {/tex}

{tex} 1.46 \times 10 ^ { 6 } \mathrm { m } / \mathrm { s } {/tex}

B

{tex} 0.73 \times 10 ^ { 6 } \mathrm { m } / \mathrm { s } {/tex}

C

{tex} 3.0 \times 10 ^ { 8 } \mathrm { m } / \mathrm { s } {/tex}

D

{tex} 2.92 \times 10 ^ { 6 } \mathrm { m } / \mathrm { s } {/tex}

Explanation

Q 11.    

Correct4

Incorrect-1

An electron in the hydrogen atom jumps from excited state n to the ground state. The wavelength so emitted illuminates
a photosensitive material having work function 2.75 eV. If the stopping potential of the photoelectron is {tex} 10 \mathrm { V } , {/tex} the value of {tex} \mathrm { n } {/tex} is

A

3

4

C

5

D

2

Explanation

Q 12.    

Correct4

Incorrect-1

The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true?

Its kinetic energy increases and its potential energy decreases.

B

Its kinetic energy decreases, potential energy increases.

C

Its kinetic and its potential energy increases.

D

Its kinetic, potential energy decrease.

Explanation



Q 13.    

Correct4

Incorrect-1

An energy of 24.6{tex} \mathrm { eV } {/tex} is required to remove one of the electrons from a neutral helium atom. The energy in (eV)
required to remove both the electrons from a neutral helium atom is

A

38.2

B

49.2

C

51.8

79

Explanation



Q 14.    

Correct4

Incorrect-1

One of the lines in the emission spectrum of {tex} \mathrm { Li } ^ { 2 + } {/tex} has the same wavelength as that of the {tex} 2 ^ { \text {nd } } {/tex} line of Balmer series in
hydrogen spectrum. The electronic transition corresponding to this line is {tex} \mathrm { n } = 12 \rightarrow \mathrm { n } = \mathrm { x } {/tex} . Find the value of {tex} \mathrm { x } {/tex} .

A

8

6

C

7

D

5

Explanation



Q 15.    

Correct4

Incorrect-1

If the atom {tex} _ { 100 } F m ^ { 257 } {/tex} follows the Bohr model and the radius of {tex} _ { 100 } \mathrm { Fm } ^ { 257 } {/tex} is {tex} n {/tex} times the Bohr radius, then find {tex} n {/tex}

A

100

B

200

C

4

{tex}1 / 4 {/tex}

Explanation

Q 16.    

Correct4

Incorrect-1

The energy of He' in the ground state is {tex} - 54.4 {/tex} eV, then the energy of {tex} \mathrm { Li } ^ { + + } {/tex} in the first excited state will be

{tex} - 30.6 \mathrm { eV } {/tex}

B

27.2{tex} \mathrm { eV } {/tex}

C

{tex} - 13.6 \mathrm { eV } {/tex}

D

{tex} - 27.2 \mathrm { eV } {/tex}

Explanation

Q 17.    

Correct4

Incorrect-1

If the angular momentum of an electron in an orbit is {tex} \mathrm { J } {/tex} then the K.E. of the electron in that orbit is

{tex} \frac { \mathrm { J } ^ { 2 } } { 2 \mathrm { mr } ^ { 2 } } {/tex}

B

{tex} \frac { \mathrm { J } \mathrm { v } } { \mathrm { r } } {/tex}

C

{tex} \frac { \mathrm { J } ^ { 2 } } { 2 \mathrm { m } } {/tex}

D

{tex} \frac { \mathrm { J } ^ { 2 } } { 2 \pi } {/tex}

Explanation



Q 18.    

Correct4

Incorrect-1

Suppose an electron is attracted towards the origin by a force {tex} \frac { k } { r } {/tex} where {tex} ^ { \prime } k ^ { \prime } {/tex} is a constant and {tex} ^ { \prime } r ^ { \prime } {/tex} is the distance of the electron from the origin. By applying Bohr model to this system, the radius of the {tex} n ^ { \text {th } } {/tex} orbital of the electron is found to be {tex} ^ {\prime } r _ { n } ^ { \prime } {/tex} and the kinetic energy of the electron to be {tex} ^ {\prime } T _ { n } ^ { \prime } {/tex} Then which of the following is true?

A

{tex} T _ { n } \propto \frac { 1 } { n ^ { 2 } } , r _ { n } \propto n ^ { 2 } {/tex}

{tex} T _ { n } {/tex} independent of {tex} n , r _ { n } \propto n {/tex}

C

{tex} T _ { n } \propto \frac { 1 } { n } , r _ { n } \propto n {/tex}

D

{tex} T _ { n } \propto \frac { 1 } { n } , r _ { n } \propto n ^ { 2 } {/tex}

Explanation

Q 19.    

Correct4

Incorrect-1

In Hydrogen spectrum, the wavelength of {tex} \mathrm { H } _ { \alpha } {/tex} line is 656{tex} \mathrm { nm } {/tex} , whereas in the spectrum of a distant galaxy, {tex} \mathrm { H } _ { \alpha } {/tex} line wavelength is {tex} 706 \mathrm { nm } . {/tex} Estimated speed of the galaxy with respect to earth is

A

{tex} 2 \times 10 ^ { 8 } \mathrm { m } / \mathrm { s } {/tex}

{tex} 2 \times 10 ^ { 7 } \mathrm { m } / \mathrm { s } {/tex}

C

{tex} 2 \times 10 ^ { 6 } \mathrm { m } / \mathrm { s } {/tex}

D

{tex} 2 \times 10 ^ { 5 } \mathrm { m } / \mathrm { s } {/tex}

Explanation



Q 20.    

Correct4

Incorrect-1

In the hydrogen atom, an electron makes a transition from
{tex} \mathrm { n } = 2 {/tex} to {tex} \mathrm { n } = 1 . {/tex} The magnetic field produced by the circulating electron at the nucleus

A

decreases 16 times

B

increases 4 times

C

decreases 4 times

increases 32 times

Explanation

Q 21.    

Correct4

Incorrect-1

What is the radius of iodine atom (At.no. 53, mass no. 126)

{tex} 2.5 \times 10 ^ { - 11 } \mathrm { m } {/tex}

B

{tex} 2.5 \times 10 ^ { - 9 } \mathrm { m } {/tex}

C

{tex} 7 \times 10 ^ { - 9 } \mathrm { m } {/tex}

D

{tex} 7 \times 10 ^ { - 6 } \mathrm { m } {/tex}

Explanation

Q 22.    

Correct4

Incorrect-1

When an {tex} \alpha {/tex} -particle of mass 'm' moving with velocity 'v' bombards on a heavy nucleus of charge 'Ze', its distance of closest approach from the nucleus depends on m as:

{tex} \frac { 1 } { m } {/tex}

B

{tex} \frac { 1 } { \sqrt { m } } {/tex}

C

{tex} \frac { 1 } { m ^ { 2 } } {/tex}

D

{tex} \mathrm { m } {/tex}

Explanation



Q 23.    

Correct4

Incorrect-1

The ionization energy of the electron in the hydrogen atom in its ground state is 13.6{tex} \mathrm { eV } {/tex} . The atoms are excited to higher
energy levels to emit radiations of 6 wavelengths. Maximum wavelength of emitted radiation corresponds to the transition between

A

{tex} \mathrm { n } = 3 {/tex} to {tex} \mathrm { n } = 1 {/tex} states

B

{tex} \mathrm { n } = 2 {/tex} to {tex} \mathrm { n } = 1 {/tex} states

{tex} \mathrm { n } = 4 {/tex} to {tex} \mathrm { n } = 3 {/tex} states

D

{tex} \mathrm { n } = 3 {/tex} to {tex} \mathrm { n } = 2 {/tex} states

Explanation



Q 24.    

Correct4

Incorrect-1

The wavelengths involved in the spectrum of deuterium {tex} \left( \begin{array} { c } { 2 } \\ { 1 } \end{array}D \right) {/tex} are slightly different from that of hydrogen spectrum, because

A

the size of the two nuclei are different

B

the nuclear forces are different in the two cases

the masses of the two nuclei are different

D

the attraction between the electron and the nucleus is differernt in the two cases

Explanation



Q 25.    

Correct4

Incorrect-1

An electron in hydrogen atom makes a transition {tex} n _ { 1 } \rightarrow n _ { 2 } {/tex} where {tex} n _ { 1 } {/tex} and {tex} n _ { 2 } {/tex} are principal quantum numbers of the two states. Assuming Bohr's model to be valid the time period of the electron in the initial state is eight times that in the final state. The possible values of {tex} n _ { 1 } {/tex} and {tex} n _ { 2 } {/tex} are

{tex} n _ { 1 } = 4 {/tex} and {tex} n _ { 2 } = 2 {/tex}

B

{tex} n _ { 1 } = 6 {/tex} and {tex} n _ { 2 } = 2 {/tex}

C

{tex} n _ { 1 } = 8 {/tex} and {tex} n _ { 2 } = 1 {/tex}

D

{tex} n _ { 1 } = 8 {/tex} and {tex} n _ { 2 } = 2 {/tex}

Explanation