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Across 1. a group 2 metals 5. the small, dense center of positive charge in an atom. 6. the modern concept of the atom as having a dense center of positive charge (the nucleus) and electrons moving around the outside. 9. fundamental unit of which elements are composed 11. a substance which contains composition that can be broken down into elements by chemical processes. 13. a postive ion 14. a group 1 metals 16. several series of elements in which inner orbitals (d or f orbitals) are being filled. 17. an element that has both metallic and nonmetallic properties. 18. positively charged particle in an atomic nucleus. 19. the number of protons in a nucleus. Z=the atomic number (the number of protons) 20. negatively charged particle that occupies space around the nucleus of an atom. 22. 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. 24. Elements are made of tiny particles called atoms. 2. All atoms of a given element are identical. 3. The atoms of a given element are different from those of any other element. 4. Atoms of one lement can combine with atoms of other elements to form compounds. A given compund always has the same relative numbers and types of atoms. 5. Atoms are indivisible in chemical processes. that is, atoms are not created or destroyed in chemcial reactions. a chemical reaction simply changes the way the atoms are grouped together. 25. set of abbreviated symbols for the chemical elements. 26. a negative ion 27. atoms of the same element (the smae number of protons) tht have different numbers of neutrons. They have identical atomic numbers but different mass numbers. 28. a group 7 element 29. the sum of the number of neutrons and the number of protons in a given nucleus. A=the mass number (sum of protons and nuetrons)

Down 2. particle in an atomic nucleus with a mass approximately equal to that of the proton but with no charge. 3. negatively charged particle that occupies thte space around the nucleus of an atom 4. a group 8 element 7. chart showing all the elements arranged in columns in such a way that all the elements in a given column exhibit similar chemical properties. 8. a compound that results when a metal reacts with a nonmetal to form cations and anions. 10. vertical columns of elements having the same valence electron configuration and similar chemical properties. 12. a molecule composed of two atoms. 15. an atom or a group of atoms that has a net positive or negative charge 21. element that gives up electrons relatively easily and is tyically lustrous, malleable, and a good conductor of heat and electricity 23. an element that does not exhibit metallic characteristics. chemically, a typical nonmetal accepts electrons froma metal.