Ch10_appendix_B

Ch10_appendix_B - Appendix B Atoms B.1 What is an atom? An...

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Appendix B Atoms B.1 What is an atom? An atom consists of an extremely small nucleus ( 核子 ) made of protons ( 質子 ) (carry positive charges) and neutrons ( 中子 ) (carry no charge), surrounded by a cloud of orbiting electrons ( 電子 ) (carry negative charges). Protons and neutrons are bounded tightly in the nucleus by nuclear force ( 核力 ) . Electrons are bounded loosely to the nucleus by electric force (attractive force between the negatively - charged electrons and the positively -charged protons). The size of the nucleus is only about 1/100,000 of the atom, but a proton (or a neutron) is about 2000 times more massive than an electron. Atoms of different elements ( ) have different numbers of protons in their nuclei. e.g., A hydrogen atom (the lightest and the simplest element) has 1 proton, a helium atom has 2 protons (Fig. B-1), a carbon atom has 6 protons, etc. Fig. B-1
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Ch10_appendix_B - Appendix B Atoms B.1 What is an atom? An...

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