Tag: change in nucleus due to radioactive decay

Questions Related to change in nucleus due to radioactive decay

In $\beta^-$ decay, a

  1. neutron converts into a proton emitting antineutrino.

  2. neutron converts into a proton emitting neutrino.

  3. proton converts into a neutron emitting antineutrino.

  4. proton converts into a neutron emitting neutrino.


Correct Option: A
Explanation:

The reaction of beta decay is shown as :

$n \rightarrow p + e^- + \bar{\nu} _e$               (antineutrino)

So, in a $\beta-$ decay, a neutron converts into a proton emitting antineutrino.

option (A) is correct.

The number of $\beta$-particles, if a radioactive element $ _{90}X^{238}$ decays into $ _{83}Y^{222}$ is :

  1. $4$

  2. $6$

  3. $2$

  4. $1$


Correct Option: D

Which of the following nuclei is produced when a $ _{92}U^{238}$ nucleus undergoes a $(d, 2n)$ reaction followed by a beta decay?

  1. $ _{93}Np^{238}$

  2. $ _{94}Pu^{239}$

  3. $ _{94}Pu^{238}$

  4. $ _{92}U^{238}$


Correct Option: C

In which of the following processes, the number of protons in the nucleus increase?

  1. $\alpha-decay$

  2. $\beta^--decay$

  3. $\beta^+-decay$

  4. k-capture


Correct Option: B
Explanation:

${ \beta  }^{ - }\quad decay$ :
Example: $ _{ 6 }^{ 14 }{ C }\longrightarrow _{ 7 }^{ 14 }{ N }+{ e }^{ - }+\bar { { v } _{ e } }$
Atomic number increases by 1 unit, which implies increase in proton.

Atomic masses of two isobars $ _{29}^{63}Cu$ and $ _{30}^{64}Zn$ are $63.9298 u$ and $63.9292 u$, respectively. It can be concluded from this data that

  1. both the isobars are stable

  2. $^{64}Zn$ is radioactive, decaying to $^{64}Cu$ through $\beta-decay$

  3. $^{64}Cu$ is radioactive, decaying to $^{64}Zn$ through $\beta-decay$

  4. $^{64}Cu$ is radioactive, decaying to $^{64}Zn$ through $\gamma-decay$


Correct Option: C
Explanation:

$Zn$ with higher no.of nucleons has a lower mass than $Cu$, which means that the binding energy/nucleon is higher in $Zn$.
Which means that $Zn$ is more stable than $Cu$.
Hence, $Cu$ will have a tendency to convert to $Zn$ by radioactive decay
$\beta$ decay to change the atomic number.
$\gamma$ decay can't help in changing the no. of protons in the nucleus.

The electron emitted in beta radiation originates from

  1. inner orbits of atoms

  2. free electrons existing in nuclei

  3. decay of a neutron in a nucleus

  4. photon escaping from the nucleus


Correct Option: C
Explanation:

The electron emitted in beta radiation may originates from neutron and it increases the atomic number $1$.

Masses of two isobars $ _{29}Cu^{64}$ and $ _{30}Zn^{64}$ are $63.9298\ u$ and $63.9292\ u$, respectively. It can be conclude from these data that

  1. Both the isobars are stable

  2. $Zn^{64}$ is radioactive, decaying to $Cu^{64}$ through $\beta-decay$

  3. $Cu^{64}$ is radioactive, decaying to $Zn^{64}$ through $\gamma-decay$

  4. $Cu^{64}$ is radioactive, decaying to $Zn^{64}$ through $\beta-decay$


Correct Option: D
Explanation:

Same no. of nucleons for $Cu^{64}$ and $Zn^{64}$
However, $M _{Cu}> M _{Zn}$
which indicates that the mass defect/ nuclear binding energy per nucleon is lesser of $Cu$, hence it will have a tendency to get to more stable form by $\beta $ decay.

Neutron decay in free space is given as follows
$ _{ 0 }{ n }^{ 1 }\longrightarrow _{ 1 }{ H }^{ 1 }+ _{ 1 }{ e }^{ 0 }+$[  ]
Then the parenthesis [  ] represents a

  1. neutrino

  2. photon

  3. antineutrino

  4. graviton


Correct Option: C
Explanation:

Since the charge is already conserved in the decay process, proton cannot be ejected.

To conserve the spin angular momentum of the initial neutron particle, an antineutrino (chargeless) is ejected.

The number of neutrons in the element L in the following nuclear changes is 
$^{238} _{92}M\, \rightarrow\, ^x _y\, N\, +\, ^4 _2\, He$
$^X _YN\, \rightarrow\, ^A _BL\, +\, 2\beta^+$

  1. $146$

  2. $144$

  3. $140$

  4. $142$


Correct Option: A
Explanation:
$ _{ 92 }^{ 238 }{ M }\rightarrow _{ y }^{ x }{ N }+ _{ 2 }^{ 4 }{ He }$
$y=92-2=90 \\ x=238-4=234$
$ _{ 90 }^{ 234 }{ N }\rightarrow _{ B }^{ A }L+2 _{ +1 }^{ o }{ \beta  }\\ B=90-2=88\\ A=234$
no. of neutrons $=234-88 \\ =146$
So, $(A)$ is correct option.

$^{11} _{6}C\, \rightarrow\,  ^{11} _{5}B$ decay produces -

  1. Positron

  2. $\beta$-particle

  3. $\alpha $-particle

  4. None of these


Correct Option: A
Explanation:

The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of $+1e$, a spin of $\cfrac{1}{2}$ and has the same mass as an electron.