Match each number to correct letter.
 1. protons plus neutron a] atomic mass 
 2. proton number b] photographic film 
 3. detects radiation c] atom 
 4. fixed shape d] electron 
 5. neutral charge e] atomic number 
 6. positive charge f] gas 
 7. occupies the whole container g] solid 
 8. measures intensity of radiation h] neutron 
 9. smallest particle to retain characteristics i] proton 
 10. negative charge j] Geiger counter