Chemistry

1. A pure substance
2. A positively charged particle in the nucleus of an atom
6. group 18 elements in the periodic table
7. an atom that has become electrically charged because of loss or gain of electrons
8. An invisible negatively charged particle that orbits the nucleus of an atom
10. horizontal row of elements in the periodic table
11. Pure substance formed when at least on metal and nonmetal combine
12. the substance that reacts with another substance
16. Pure substance formed when non-metals combine
18. a new substance produced from a chemical reaction between reactants
19. A substance that helps a chemical reaction go faster
20. Most reactive non metals
22. catalyst involved in chemical reactions in living things

1. A chemical reaction that releases energy
3. A cloudy mixture in which tiny particles of one substance are held within another
4. A chemical reaction that absorbs energy
5. a table in which the elements are organized
9. a shiny,malleable,ductile element
13. Mass of an atom
14. The sum of the number of protons and neutrons in an atom
15. Vertical column of elements in the periodic table
16. a Element that has both metallic and non metallic properties
17. A slow chemical change between metal and oxygen
21. Positively charged centre of an atom