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Across 2. group 2 elements. (3 words) 5. the sum of protons and neutrons. (2 words) 7. positive ion. 9. a compound that results when a metal reacts with a nonmetal to form cations and anions. (2 words) 10. a representation of a molecule in which the symbols for the elements are used to indicate the types of atoms present and subscripts are used to show the relative numbers of atoms. (2 words) 11. the number of protons. (2 words) 13. abbreviations for the chemical elements. (2 words) 14. molecules that are made up of two atoms. (2 words) 16. positively charged. 17. the modern concept of the atom as having a dense center of positive charge (the nucleus) and electrons moving around the outside. (2 words) 19. the small, dense center of positive charge in an atom. 20. a chart showing all the elements arranged in columns in such a was that all the elements in a given column exhibit sililar chemical properties. (2 words) 22. an element that has both metallic and non-metallic properties. 23. atoms with the same number of protons but different numbers of neutrons. 24. a distinct substance that is composed of the atoms of two or more elements and always contains exactly the same relative masses of those elements. 25. negative ion. 26. families of elements with similar chemical properties that lie in the same vertical column on the periodic table.

Down 1. a principle that means that a given compound always has the same composition, regardless of where it comes from. (4 words) 2. first column of elements (group 1). (2 words) 3. several series of elements in which inner orbitals (d or f orbitals) are being filled. (2 words) 4. group 7 elements. 6. an atom or a group of atoms that has a net positive or negative charge. 8. group 8 elements. (2 words) 12. an element that does not exhibit metallic characteristics. chemicallu, a typical monmetal accepts electrons from a metal. 15. (same as metalloids) includes silicon, germanium, arsenic, antimony, and tellerium. 17. neutral charge. 18. negative particles. 21. an element that gives up electrons relatively easily and is typically lustrous, malleable, and a good conductor of heat and electricity.