Chemistry

4. atom that has become electrically charged because it has lost or gained electrons
5. substance made up of only one type of atom
6. number of protons in the nucleus of one atom of an element
7. pure substance formed when at least one metal and one non metal combine
10. neutral particle in the nucleus of an atom
12. pure substance formed when non-metals combine
14. group 18 elements in the periodic table the most stable and un reactive elements
15. horizontal row of elements in the periodic table
16. combination of symbols that represent a compound
19. neutral particle in the nucleus of an atom

1. vertical column of elements in the periodic table
2. invisible negatively charged particle that orbits the nucleus of an atom.
3. catalyst involved in chemical reactions in living things
6. group two elements in the periodic table their reactivity is not as strong as the alkali metals
8. group one elements in the periodic table not including hydrogen
9. invisible negatively charged particle that orbits the nucleus of an atom
11. metal that has both metallic and non-metallic properties
12. the sum of the protons and neutrons in an atom
13. description of a substance that can be pounded or rolled into sheets
15. positively charged atom in the nucleus of an atom
16. substance that helps a chemical reaction to proceed more qiucklly
17. group of atoms joined by covalent bonds
18. the smallest part of an element that is representative of that element