Atoms and nuclei > ionising air

A candle flame is electrically conductive. An EHT will visibly separate its free charges, causing a current to flow in an external circuit.

A match flame will ionise the air. Use this to show ionisation and how it can be detected by charging an electroscope.

A radioactive source produces radiation that will ionise the air. The conducting air completes a circuit to charge an electroscope. Use the circuit to show the ionising effect of the radiation and present it as a means of detecting ionising radiation.