Chemistry crossword

1. a system of easy-to-see warning symbols on hazardous materials
6. the ability of a substance to conduct electricity or heat
8. change in the appearance or state of a substance that does not change the composition
9. a reaction that takes place when two or more substances react to form new substances
11. mass of one atom of an element calculated from the total number of protons, neutrons, electrons of that atom
12. characteristics that describe a particular substance (e.g. colour, lustre, melting point)
13. combination of symbols that represent a compound
15. group 1 elements in the periodic table, not including hydrogen
16. anything that has mass and occupies space
18. horizontal row of elements in the periodic table
19. pure substance formed when at least one metal and one non-metal combine
23. positively charged centre of an atom; contains protons and neutrons

2. group 17 elements in the periodic table
3. a table in which the elements are organized by their physical and chemical properties
4. netrual particle in the nucleus of an atom
5. measure of one atomic mass
7. pure substance formed when non-metals combine
8. made of only one kind of matter
10. occurs when two or more materials react and create new materials
12. group of atoms acting as one
14. group of atoms joined by covalent bonds
17. vertical column of elements in the periodic table
20. a chemical reaction that occurs when oxygen reacts with a substance to form a new substance and give off energy
21. positively charged particle in the nucleus of an atom
22. amount of mass in a given volume of a substance