(a) Define nucleon number
(b) A radioactive isotope of Americium (Am —241) decays into a nucleus of Neptunium (Np — 237) and an alpha (\(\alpha\)) particle as shown in the nuclear equation below. \(^{241}_{95}Am\) \(\to\) \(^{237}_{c} + ^b_a \alpha\)
(i) State the number of neutrons in the nucleus of Americium — 241.
(ii) Determine the values of a,b and c.
(c)(i) Why are y-rays not deflected by electromagnetic field?
(ii) State two properties of gamma rays that make them suitable for sterilizing medical equipment.
(d) A sample of radioactive substance was found to be left with h of its initial count rate after 110 years. Calculate its decay constant.
(a) Nucleon number is the total number of protons and neutrons in the nucleus of an atom.
(b)(i) Number of neutrons in the nucleus of Americium = 241 - 90 =146.
(ii) a = 2
b = 4
c = 95 - 2
= 93.
(c)(i) Y-ray are electrically neutral or carry no charge.
(ii) properties of gamma rays that makes them suitable for medical sterilization of equipment are:
(1) Possession of strong penetrating power.
(2) Posession of low ionizing power.
(d) \(\frac{N}{N_o} = (\frac{1}{2})^a = \frac{1}{32} = (\frac{1}{2})^a\) = (\(\frac{1}{2})^5\)
But T\(_\frac{1}{2}\) = \(\frac{t}{n} = \frac{110}{5}\) = 22 years
Hence \(\lambda\) = \(\frac{0.693}{T_{\frac{1}{2}}} = \frac{0,693}{22}\)
Decay constant \(\lambda\) 3.2 x 10\(^{-2}\) per year
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