1. $α$ -particale consists of : ⇒ ( NEET 2019)

A. 2 electrons, 2 protons and 2 neutrons

B. 2 electrons and 4 protons only

C. 2 protons only

D. 2 protons and 2 neutrons only

The Correct Answer is Option (D)

Since, $α$ -particle is equivalent to He-atom nucleus, hence it has two protons and two neutrons only.

2. A nucleus of uranium decays at rest into nuclei of thorium and helium. Then ⇒ (AIPMT 2015)

A. The helium nucleus has more momentum than the thorium nucleus.

B. The helium nucleus has less kinetic energy than the thorium nucleus.

C. The helium nucleus has more kinetic energy than the thorium nucleus.

D. The helium nucleus has less momentum than the thorium nucleus.

The Correct Answer is Option (C)

In an explosion a body breaks up into two pieces of unequal masses both part will have numerically equal momentum and lighter part will have more velocity.

U $\to$ Th + He

KE_Th = $\frac{P^{2}}{2 m_{T h}}$

KE_He = $\frac{P^{2}}{2 m_{H e}}$

since m_He is less so KE_He will be more.

3. $α$ -particles, $β$ -particles and $γ$ -rays are all having same energy. Their penetrating power in a given medium in increasing order will be ⇒ (NEET 2013 (Karnataka))

A. $γ$ , $α$ , $β$

B. $α$ , $β$ , $γ$

C. $β$ , $α$ , $γ$

D. $β$ , $γ$ , $α$

The Correct Answer is Option (B)

For a given energy, $γ$ -rays has highest penetrating power and $α$ -particles has least penetrating power.

4. A nucleus $_{n}^{m} X$ emits one $α$ particle and two $β$ particles. The resulting nucleus is ⇒ ( AIPMT 2011 Prelims)

A. $_{n - 4}^{m - 6} Z$

B. $_{n}^{m - 6} Z$

C. $_{n}^{m - 4} X$

D. $_{n - 2}^{m - 4} Y$

The Correct Answer is Option (C)

$α$ -particle is ₂He⁴

In $β$ emission, the neutron gets converted to proton and electron

_nX^m $\overset{1 α}{⟶}$ _{n - 2}Y^{m - 4} $\overset{2 β}{⟶}$ _nZ^{m - 4}

5. In the nuclear decay given below

$_{Z}^{A} X \to_{Z + 1}^{A} Y \to_{Z - 1}^{A - 4} B^{*} \to_{Z - 1}^{A - 4} B,$

the particles emitted in the sequence are ⇒ (AIPMT 2009)

A. $γ$ , $β$ , $α$

B. $β$ , $γ$ , $α$

C. $α$ , $β$ , $γ$

D. $β$ , $α$ , $γ$

The Correct Answer is Option (D)

First X decays by $β$ ^–. Y emits $α$ resulting in the excited level of B which in turn emits a $γ$ ray.

$∴$ $β$ , $α$ , $γ$ is the answer.

6. The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter is an ⇒ ( AIPMT 2009)

A. isomer of parent

B. isotone of parent

C. isotope of parent

D. isobar of parent

The Correct Answer is Option (C)

$_{Z}^{A} X \overset{2 β^{-}}{⟶}_{Z + 2}^{A} Y_{1} \overset{α}{⟶}_{Z}^{A + 4} Y_{2}$

The resultant daughter is an isotope of the original parent nucleus.

7. In a radioactive decay process, the negatively charged emitted $β$ -particles are⇒ (AIPMT 2007)

A. the electrons produced as a result of the decay of neutrons inside the nucleus

B. the electrons produced as a result of collisions between atoms

C. the electrons orbitting around the nucleus

D. the electrons present inside the nucleus

The Correct Answer is Option (C)

In beta minus decay ( $β$ ^–), a neutron is transformed into a proton, and an electron is emitted from the nucleus along with antineutrino.

n = p + e^$-$ + $\overset{―}{ν}$

8. A nuclear reaction given by

_ZX^A $\to$ _z+1Y^A + _{$-$ 1}e⁰ + $\overset{―}{v}$ represents ⇒ ( AIPMT 2003)

A. $β$ -decay

B. $γ$ -decay

C. fusion

D. fission

The Correct Answer is Option (A)

It represents $β$ -decay.

As Emission of electron (e^– ) + antineutrino ( $\overset{―}{ν}$ ) $\Rightarrow$ $β$ -decay.

9. Which rays contain (positive) charged particles ? ⇒ (AIPMT 2001)

A. $α$ -rays

B. $β$ -rays

C. $γ$ -rays

D. X-rays

The Correct Answer is Option (A)

$α$ -rays contain Helium nuclei which contains 2 unit of positive charge.

10. X(n, $α$ ) $_{3}^{7}$ Li, then X will be ⇒ (AIPMT 2001)

A. $_{5}^{10}$ B

B. $_{5}^{9}$ B

C. $_{5}^{11}$ Be

D. $_{2}^{4}$ He.

The Correct Answer is Option (A)

$_{5}^{10}$ B + $_{0}^{1}$ n $\to$ $_{2}^{4}$ He + $_{3}^{7}$ Li

⇒ Nuclei

Topic 3 : Radioactive Decay