上物理課了?。好總€原子有三部分組成質子、中子和電子，質子帶正電荷，電子帶負電荷，中子不帶電荷；質子和中子包裹在原子核里。質子和中子裝在原子核里，而電子在外面繞著旋轉。質子的數量決定一個原子的化學特性~~~
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Let us pause for a moment and consider the structure of the atom as we know it now. Every atom [-1-] three kinds of elementary particles: protons, which have a positive electrical charge; electrons, which have a negative electrical charge; and neutrons, which have no charge. Protons and neutrons [-2-] the nucleus, while electrons spin around outside. [---3---] An atom with one proton is an atom of hydrogen, one with two protons is helium, with three protons is lithium, [-4-] . Each time you add a proton you get a new element. ([---5---], you will sometimes see it written that it is the number of electrons that defines an element; it comes to the same thing. [---6---])
Neutrons don't influence an atom's identity, but they do add to its mass. [---7---] Add a neutron or two and you get an isotope. The terms you hear [-8-] dating techniques in archeology refer to isotopes--carbon-14, for instance, which is an atom of carbon with six protons and eight neutrons ([-9-]).
is made from are packed into The number of protons is what gives an atom its chemical identity. and so on up the scale Because the number of protons in an atom is always balanced by an equal number of electrons The way it was explained to me is that protons give an atom its identity, electrons its personality. The number of neutrons is generally about the same as the number of protons, but they can vary up and down slightly. in reference to the 14 being the sum of the two
讓我們稍停片刻，先來考慮一下現(xiàn)在我們所知道的原子結構。每個原子都由三種基本粒子組成：帶正電荷的質子，帶負電荷的電子，以及不帶電荷的中子。質子和中子裝在原子核里，而電子在外面繞著旋轉。質子的數量決定一個原子的化學特性。有一個質子的原子是氫原子；有兩個質子的原子是氦原子；有三個質子的原子是鋰原子；如此往上增加。你每增加一個質子就得到一種新元素。（由于原子里的質子數量總是與同樣數量的電子保持平衡，因此你有時候會發(fā)現(xiàn)有的書里以電子的數量來界定一種元素，結果完全一樣。有人是這樣向我解釋的：質子決定一個原子的身份，電子決定一個原子的性情。） 中子不影響原子的身份，但卻增加了它的質量。一般來說，中子數量與質子數量大致相等，但也可以稍稍多一點或少一點。增加或減少一兩個中子，你就得到了同位素。考古學里就是用同位素來確定年代的--比如，碳－14是由6個質子和8個中子組成的碳原子（因為二者之和是14）。