Composition of the atom and nuclear reactions
Answers are for parents and teachers.
1
How many neutrons are in the ²³⁵U nucleus (Z = 92)?
143
2
Which nucleus forms when ²²⁸Th (Z = 90) undergoes α-decay?
²²⁴Ra (Z = 88).
3
Natural magnesium is ²⁴Mg (79 %), ²⁵Mg (10 %) and ²⁶Mg (11 %). Find Aᵣ(Mg).
24.32
4
²³⁵U + n → ¹⁴⁴Ba + X + 3n. Find the mass number and atomic number of X (Z = 56 for Ba).
From 236 = 144 + A + 3, A = 89; Z = 92 – 56 = 36, so X is ⁸⁹Kr.
5
Why do only specialists work with radioactive preparations?
Radiation damages living tissue, so shielding, monitoring and special authorisation are required.