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Across 4. the abreviations on the periodic table are called chemical________ 7. negatively charged particles 8. table used to organize atoms 11. water is made of hydrogen and _________ 12. sodium chloride (2 words) 13. charged atom 15. scientist who first discovered how molecules are held together (3 words) 17. carbon-14 is a _______isotope found in living things 20. formed when atoms share two electrons (2 words) 25. one of the three most comon elements in living things 27. positively charged ion in living things 30. NaCl (2 words) 31. particles with no charge 32. changing the number of _______in an atom, changes its stability 33. one of the most common elements in living things

Down 1. provides energy for living cells 2. MOLECULES are held together by positive and negative _______forces 3. contains protons and neutrons 5. electrical attraction between oppositely charge ATOMS (2 words) 6. pure substance 9. negatively charged ion in living things 10. electrons are moving in ________ levels 14. bond formed when atoms share electrons 16. process used to separate water into pure elements 18. building blocks of matter 19. safe and environmentally friendly solvents (2 words) 21. contains one proton 22. climb smooth surfaces due to electrical attractions 23. positively charged particles 24. scientists use this to calculate age of a once living object 26. held together by covalent bonds 28. pure substance of combined elements 29. atoms become __________ with a full outer energy level