Complete the following sentences:

(a) The mass number and atomic number of an element are not changed when it emits ……………

(b) The atomic number of a radioactive element is not changed when it emits ……………

(c) During the emission of a beta particle, the …………… number remains same.

Complete the following nuclear changes —

(a) $_{x}^{a}\text{P} \longrightarrow Q + _{-1}^{0}\text{β}$
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(b) $_{92}^{238}\text{U} \longrightarrow \space _{90}^{234}\text{Th} + …… + \text{energy}$

(c) $_{92}^{238}\text{P} \overset{\alpha} \longrightarrow \text{Q} \overset{\beta} \longrightarrow \text{R} \overset{\beta} \longrightarrow \text{S}$

(d) {Z}^{A}\text{X} \overset{\alpha} \longrightarrow \text{X}{1} \overset{\gamma} \longrightarrow \text{X}{2} \overset{2\beta} \longrightarrow \text{X}{3}

(e) $\text{X} \overset{\beta} \longrightarrow \text{X}${1} \overset{\alpha} \longrightarrow \text{X}{2} \overset{\alpha} \longrightarrow \space {69}^{172}\text{X}{3}

Which of the following is the radio isotope in each pair (a), (b) and (c) ?

(a) ${}_6^{12}\text{C}${6}^{12}\text{C}, ${6}^{14}\text{C}$

(b) ${}_{15}^{30}\text{P}${15}^{30}\text{P}, ${15}^{32}\text{P}$

(c) ${}_{19}^{39}\text{K}${19}^{39}\text{K}, ${19}^{40}\text{K}$

Give reason for your answer.

Name the three constituents of an atom and state mass and charge of each. How are they distributed in an atom?