Question

An atomic nucleus A is composed of 84 protons and 128 neutrons.
(i)The nucleus A emits an alpha particle and is transformed into nucleus B. What is the composition of nucleus B?
(ii) The nucleus B emits a beta particle and is transformed into a nucleus C. What is the composition of nucleus C?
(iii) Does the composition of nucleus C change if it emits gamma radiations?
[5 MARKS]

Answer 1

Part (i) : 2 Marks
Part (ii) : 2 Marks
Part (iii) : 1 Mark

(i) In nucleus B atomic no. is decreased by 2 and mass no. is decreased by 4. Thus, the resulting nucleus has 2 protons and 2 neutrons less than parent (A) nucleus.
${}_{84}^{212}A\to {}_2^{4}He+{}_{82}^{208}B$

(ii) While emitting a $\beta$ - particle, the number of nucleons in nucleus C remains same but the number of neutrons is decreased by one and the no. of protons is increased by one.
${}_{81}^{208}B\to {}_{-1}^{0}e+{}_{83}^{208}C$

(iii) There is no change in composition except emitting y radiation.