A nuclear museum displays an information panel about uranium-238. Fig. 1 shows the first change in one decay route. The panel has left two boxes blank so th...
Question 1 Report
A nuclear museum displays an information panel about uranium-238. Fig. 1 shows the first change in one decay route. The panel has left two boxes blank so that visitors can complete the nuclear equation. The uranium isotope emits an alpha particle from its nucleus.
(a) Complete the two missing mass numbers and two missing proton numbers in Fig. 1. [2]
(b) State the number of protons in an alpha particle. [1]
(c) Calculate the number of neutrons in a uranium-238 nucleus. [2]
(d) Explain how the completed equation demonstrates conservation of nucleon number. [1]
Answer Details
(a) Alpha decay emits a \(^{4}_{2}\text{He}\) nucleus, so the completed equation is:
\[^{238}_{92}\text{U}\rightarrow{}^{234}_{90}\text{Th}+{}^{4}_{2}\text{He}\]
The thorium nucleus is \(^{234}_{90}\text{Th}\) and the alpha particle is \(^{4}_{2}\text{He}\). [2]
(b) An alpha particle has 2 protons. [1]
(c) Neutron number equals mass number minus proton number:
\[238-92=146\]
A uranium-238 nucleus has 146 neutrons. [2]
(d) The nucleon numbers balance because:
\[234+4=238\]
The total nucleon number is the same on both sides of the equation. [1]
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