Across
- 1. The very tiny middle part of the atom which contains protons and neutrons (except for hydrogen which just has 1 proton)
- 5. Different forms of the same element, which have the same number of protons but different numbers of neutrons
- 8. The number of protons AND neutrons added together in an atom. The top number when you write an element in symbol form
- 9. The substance in a nuclear reactor which slows down neutrons and makes them more likely to hit other uranium nuclei.
- 11. What is given off by radioactive atoms, and which causes ionisation (the knocking out of electrons from other matter)
- 15. A negatively charged particle
- 17. Rods which are lowered into a nuclear reactor to slow the reaction down
Down
- 1. A particle in the nucleus (i.e. a proton or a neutron)
- 2. A piece of apparatus for detecting ionising radiation
- 3. A nucleus with electrons orbiting, with no overall charge
- 4. When a neutron from one fission reaction goes on to hit another uranium nucleus and cause it to split (and so on)
- 6. A radioactive isotope which is used to follow the path of the flow of a liquid or gas
- 7. A positively charged particle
- 10. Unstable
- 12. The number of protons in an atom, and its position in the Periodic Table. The bottom number when you write an element in symbol form
- 13. The splitting of uranium-238 into to smaller atoms and a few neutrons
- 14. The amount of ionising radiation emitted per second, measured in becquerels (Bq), so 1 Bq is one bit of radiation per second.
- 16. The time it takes for the activity to fall to half of its original value (and therefore also the number of radioactive atoms to halve)
- 18. An uncharged particle (about the same mass as a proton)