a) Calculate the number of α-particles and β-particles emitted when $^{238}_{92}$U changes to $^{206}_{82}$Pb. b) What is meant by K-capture in nuclear chemistry?

CBSE Class 12 · 2006 · Chemical KineticsShort Answer

a) Calculate the number of α-particles and β-particles emitted when

_{92}^{238}

U changes to

_{82}^{206}

Pb.
b) What is meant by K-capture in nuclear chemistry?

Answer: (a) 8 α and 6 β particles. (b) Capture of a K-shell electron by the nucleus (p + e⁻ → n), accompanied by X-ray emission.

(a) Let

x

α and

y

β particles be emitted.
Mass balance:

238 = 206 + 4 x \Rightarrow x = 8

.
Charge balance:

92 = 82 + 2 x - y \Rightarrow 92 = 82 + 16 - y \Rightarrow y = 6

8 α and 6 β particles

(b) K-capture (electron capture): the nucleus captures an electron from the innermost K shell; a proton combines with it to form a neutron (

p + e^{-} \to n

), lowering the atomic number by one. The vacancy created in the K shell is filled by outer electrons, emitting characteristic X-rays.

CBSE Class 12 Board · 2006 · Subjective