Argon makes up nearly 1% of the air. It was not discovered until 1894, long after chlorine and potassium were known.
An argon atom has atomic number 18 and mass number 40.
Give the number of protons, neutrons and electrons in this argon atom.
Give the electronic configuration of an argon atom.
A chlorine atom has the electronic configuration 2.8.7 and a potassium atom has the electronic configuration 2.8.8.1. Explain why argon is unreactive but chlorine and potassium are reactive.
Suggest why argon was discovered much later than chlorine and potassium.
A helium atom has only two electrons. Explain why helium is also unreactive.
38 exam-style questions on Edexcel GCSE Chemistry 7.3 Group 0, covering 7.3.1 The noble gases. Each one has a worked solution and a mark scheme showing where the marks go.