Question Details

List-I shows different radioactive decay processes and List-II provides possible emitted particles. Match each entry in List-I with an appropriate entry from List-II, and choose the correct option.


List-I List-II
(P) U 92 238 Pa 91 234 (1) one α particle and one β+ particle
(Q) Pb 82 214 Pb 82 210 (2) three β particles and one α particle
(R) Tl 81 210 Pb 82 206 (3) two β particles and one α particle
(S) Pa 91 228 Ra 88 224 (4) one α particle and one β particle
(5) one α particle and two β+ particles

Options

A

P → 4, Q → 3, R → 2, S → 1

B

P → 4, Q → 1, R → 2, S → 5

C

P → 5, Q → 3, R → 1, S → 4

D

P → 5, Q → 1, R → 3, S → 2

Show Answer

Correct Answer :

Option A

P → 4, Q → 3, R → 2, S → 1

Solution :

The correct option is P → 4, Q → 3, R → 2, S → 1.

To determine the emitted particles in each radioactive decay process, we apply the conservation of mass number (A) and atomic number (Z):

1. Emitting an α particle (He24) decreases the mass number by 4 and the atomic number by 2.
2. Emitting a β particle (e10) leaves the mass number unchanged and increases the atomic number by 1.
3. Emitting a β+ particle (e+10) leaves the mass number unchanged and decreases the atomic number by 1.

Let us analyze each process step-by-step:

(P) U92238Pa91234

Change in mass number (A): 238 - 234 = 4.
This indicates the emission of 1 α particle (which reduces A by 4 and Z by 2).
After emitting 1 α particle, the atomic number becomes: 92 - 2 = 90.
The final product has an atomic number of 91, which requires an increase of 1 in Z.
This increase is achieved by emitting 1 β particle.
Hence, process (P) emits one α particle and one β particle.
Thus, P → 4.

(Q) Pb82214Pb82210

Change in mass number (A): 214 - 210 = 4.
This corresponds to the emission of 1 α particle.
After emitting 1 α particle, the atomic number becomes: 82 - 2 = 80.
The final product has an atomic number of 82, requiring an increase of 2 in Z.
This increase is achieved by emitting 2 β particles.
Hence, process (Q) emits two β particles and one α particle.
Thus, Q → 3.

(R) Tl81210Pb82206

Change in mass number (A): 210 - 206 = 4.
This corresponds to the emission of 1 α particle.
After emitting 1 α particle, the atomic number becomes: 81 - 2 = 79.
The final product has an atomic number of 82, requiring an increase of 3 in Z.
This increase is achieved by emitting 3 β particles.
Hence, process (R) emits three β particles and one α particle.
Thus, R → 2.

(S) Pa91228Ra88224

Change in mass number (A): 228 - 224 = 4.
This corresponds to the emission of 1 α particle.
After emitting 1 α particle, the atomic number becomes: 91 - 2 = 89.
The final product has an atomic number of 88, requiring a decrease of 1 in Z.
This decrease is achieved by emitting 1 β+ particle.
Hence, process (S) emits one α particle and one β+ particle.
Thus, S → 1.

Combining all the matches gives:
P → 4, Q → 3, R → 2, S → 1

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