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Across 3. The smallest particle of an element 8. a group of elements with similar chemical properties 9. any metal in group 2a of the periodic table 12. an atom or molecule which has gained or lost one or more of its valence electrons 13. a negatively charge sub atomic particles 15. a vertical column in the periodic table 18. nuetral charge 19. group of elments in which the 4f sublevel is being filled 20. an elctrons outer shell of an atom that can participate in forming chemical bonds with other atoms 21. a measure of the relative tendency of an atom to attract electrons to it self when chemically combined with another atom

Down 1. in any atom no two electrons can have all four quantum numbers the same 2. energy required to remove an electron from a gaseous atom or ion 3. one-half the distance between nuclei in a molecule consisting of identical atoms 4. an element located in group VIIA of the periodic table 5. any of the elments found in group 8 at far right of the periodic table 6. electrons enter orbitals of lowest energy first 7. horizantal row of the periodic table 9. the number of protons in the nucleus of an atom of an element 10. elementa 90 to 103 11. atoms with the same number of protons but differing nuetrons 14. postively charge sub atomic particles 16. the central of an atom 17. an amount of electons