THE ATOMIC NUCLEUS

Chapter – 19

Q.1: How many neutrons and protons do the following nuclei contain?

Nuclide	Protons	Neutrons
$^{27}_{13}Al$	13	$27 - 13 = 14$
$^{40}_{18}Ar$	18	$40 - 18 = 22$
$^{138}_{56}Ba$	56	$138 - 56 = 82$
$^{207}_{82}Pb$	82	$207 - 82 = 125$
$^{28}_{14}Si$	14	$28 - 14 = 14$
$^{238}_{92}U$	92	$238 - 92 = 146$

Q.2: Do $\alpha$, $\beta$, and gamma rays come from the same element? Why do we find all three in many radioactive samples?
Ans: A radioactive element either emits $\alpha$-particles or $\beta$-particles, but never both. Gamma radiations generally accompany $\beta$-emission and, in some cases, with $\alpha$-emission.