Across
- 1. unit mass of a proton or a neutron
- 3. radiation that is in the form of energy
- 6. smallest unit of matter
- 7. the atomic number of Na
- 9. rows in the periodic table
- 10. electrons orbit the nucleus in a cloud or .........
- 12. group 18 of the Periodic Table are the ....... gases
- 13. the number of electrons in the outermost shell of an atom
Down
- 1. radiation that is given off as a helium nuclei
- 2. when group I metals react in water they make this
- 3. chemical family organised in columns
- 4. Russian who developed the periodic table
- 5. to calculate the atomic .......... add the number of neutrons and protons
- 8. the number of neutrons in carbon
- 11. form of an element with different atomic weights
- 14. to get the atomic weight do this to the number of protons and neutrons