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Across 1. Waves transfer ____? 3. Type of waves that pass through soft body tissues but stopped by bones. 5. Type of waves that cause sunburn. 6. Part of the spectrum our eyes are sensitive to. 8. The space around the nucleus of an atom where electrons are found. 9. Neutral particle found in the nucleus of an atom. 12. Number of protons in an atom's nucleus. 13. Forms of the same element with different numbers of neutrons. 14. The sum of protons and neutrons in an atom. 15. Last name of chemisty who gave us the law of definite proportions. 16. Greek philosopher who first coined the idea of the atom. 20. A way of illustrating valence electrons. 22. Last name of scientists who discovered electrons. 23. A testable prediction to explain an observation. 24. Last name of chemisty who gave us the law of conservation of matter. 25. Type of electrons in the outermost energy level of an atom. 26. Waves with the lowest frequencies of the spectrum.

Down 1. Regions of space in which electrons can move about the nucleus. 2. The four basic elements of matter according to the ancient Greeks [no spaces between words]. 4. A fact of nature that is observed so often it is accepted as truth. 7. Type of waves that travel at the speed of light through space. 10. Small, dense, positively charged central core of an atom. 11. Positively charged subatomic particle. 17. Last name of scientist who discovered the nucleus. 18. An explanation based on many tests. 19. Type of waves with highest frequency and shortest wavelength. 21. Type of wave energy given off by the human body and other warm objects.