An analytical chemist investigates a sample of element YYY, which has an atomic number of 20.
The mass spectrometer detects two distinct isotopes of this element: one with a mass number of 40 and another with a mass number of 44.
Explain, in terms of subatomic particles, what is meant by the term isotopes. Refer to element YYY in your answer.
87 exam-style questions on Edexcel GCSE Chemistry 2.1 Atomic structure, covering 2.1.1 Development of the atomic model, 2.1.2 Structure of the atom and subatomic particles, 2.1.3 Mass number, isotopes and relative atomic mass, and 2.1.4 Calculating relative atomic mass from isotopic abundance. Each one has a worked solution and a mark scheme showing where the marks go.