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Across 1. 1. What is a change that produces one or more new substances? 3. 1. What is a neutral group of atoms joined by covalent bonds? 5. 1. What is the number of protons in the nucleus of an atom? 9. 1. What is it called when two atoms of the same element bond? 11. 1. What is it called when metal atoms transfer valence electrons to nonmetals? 13. 1. What is the positively charged particle found in an atom's nucleus? 15. 1. What is the smallest particle that can still be considered an element? 16. What is a neutral group of atoms joined by ionic bonds? 17. 1. What is a group of symbols that show the ratio of atoms in a compound or molecule? 20. 1. What is the sum of the protons and neutrons in an atom's nucleus? 21. 1. What are the vertical columns on the periodic table whose elements share similar characteristics called? 23. 1. What is it called when nonmental atoms share valence electrons? 24. 1. What are the substances you start with in a chemical reaction? 25. 1. What is it called when two pairs of electrons are shared in a covalent bond? 26. 1. What are the horizontal rows on the periodic table whose elements differ in properties?

Down 2. 1. What is the average mass of all the isotopes of an element? 4. 1. What is a chemical reaction inside a sealed, airtight container? 6. 1. What is a change in an atom's state of matter or appearance? 7. 1. What is an atom with the same number of protons but a different number of neutrons? 8. 1. What is involved in chemical bonding and determines the chemical properties of an element? 10. 1. What is an atom or group that has an electric charge due to gaining or losing electrons? 12. 1. What are the substances formed during a chemical reaction? 14. 1. What is the force of attraction that holds atoms together? 18. 1. What is it called when matter can enter from or escape to the surroundings? 19. 1. What is it called when three pairs of electrons are shared in a covalent bond? 22. 1. What is the term for how likely an atom is to bond with another atom?