| 31. | Some chemical elements are named after places on the planet earth.
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| 32. | Spectroscopy ( for example ) determines what chemical elements comprise a particular star.
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| 33. | We are made of chemical elements forged in stars and scattered through space.
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| 34. | Chemical elements up to the iron peak are produced in ordinary stellar nucleosynthesis.
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| 35. | He guessed that these lines indicated the existence of an undiscovered chemical element.
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| 36. | The new technique takes advantage of different forms, known as isotopes, of chemical elements.
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| 37. | The stolen isotopes included at least 50 chemical elements in 228 different atomic weights.
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| 38. | About 29 chemical elements play an active positive role in living organisms on Earth.
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| 39. | There exist twenty-nine chemical elements on Earth that are radioactive.
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| 40. | The company derives its name from the chemical element iridium.
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