1											2
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6
						7			8										9											10
		11
									12
		13		14
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18										19
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				21										22
					23																				24
									25							26
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														31							32
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	35
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37
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																				39

Across 1. the number of protons in the nucleus of an atom. It is a characteristic identifier of an element. 3. occupy group VIIA (17) of the periodic table. 8. the probability of finding the electron at a particular location. 11. any one of 18 vertical columns of elements. (Note that a group is often referred to as a family.) 12. one of the numerous atomic regions where electrons may be found. 15. a negatively charged particle outside of the nucleus of an atom. 16. the smallest unit of an element that retains properties of that element. 17. the energy needed to remove an electron from an atom in the gas phase. 18. the complete range of electromagnetic waves. 20. the sum of the number of protons and neutrons in an atom. 21. atom of the same element that differs in mass because it contains different numbers of neutrons. 22. occurs between groups IIIB (3) and IIB (12) in the long period of the periodic table. 27. occupy group IIA (2) of the periodic table. 29. an electrically charged particle that is formed by the gain or loss of an electron. 32. a positively charged atom or group of atoms. 34. elements in group VIIIA (18) of the periodic table. 35. a specific region of space where an electron may be found. 36. a law stating that properties of elements are periodic functions of their atomic numbers. 37. a positively charged particle in the nucleus of an atom. 38. any one of seven horizontal rows of elements in the periodic table. 39. element located on the right side of the periodic table (right of the “staircase” boundary).

Down 2. energy that is propagated as waves at the speed of light. 4. a rule predicting that atoms form the most stable molecules or ions when they are surrounded by eight electrons in their highest occupied energy level. 5. an uncharged particle, with the same mass as the proton, found in the nucleus of an atom. 6. electron in the outermost shell (principal quantum level) of an atom. 7. the measurement of intensity and energy of electromagnetic radiation. 9. the arrangement of electrons in atomic orbitals. 10. the energy released when an electron is added to an isolated atom. 13. member of the group of the periodic table designated as “A”. 14. atoms, ions, and molecules containing the same number of electrons. 16. occupy group IA (1) of the periodic table. 19. the small, dense center of positive charge in the atom. 23. a characteristic that energy can occur only in discrete units called quanta. 24. 2.99 x 108 m/s in a vacuum. 25. a stream of electrons that are given off by the cathode (negative electrode) in a cathode ray tube. 26. an element along the “staircase” boundary between metals and nonmetals; they exhibit both metallic and nonmetallic properties. 28. the mass of the atom expressed in atomic mass units. 30. element located on the left side of the periodic table (left of the “staircase” boundary). 31. set of equal-energy orbitals within a principal energy level. 33. a negatively charged atom or group of atoms.