Element X is used in fertilisers. An atom of X has a mass number of 39. Its nucleus contains one more neutron than proton.
Give the relative mass and relative charge of an electron.
Deduce the number of protons in an atom of X and identify element X.
Element X forms ions with a charge of 1+. Give the number of electrons in one of these ions.
Explain why an atom of X is neutral but its ion is charged.
The mass of a proton is 1.673 × 10-27 kg, the mass of a neutron is 1.675 × 10-27 kg and the mass of an electron is 9.11 × 10-31 kg. Calculate the percentage of the mass of an atom of X that is due to its electrons. Give your answer to three significant figures.
46 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.