An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are very small; typical sizes are around 100 picometers (a ten-billionth of a meter, in the short scale).
原子是具有化学元素性质的普通物质的最小组成单位。每一种固体、液体、气体和等离子体都是由中性或电离的原子组成的。原子非常小；典型尺寸约为100皮米。
In the long scale, a billion is a million millions [万亿] rather than a thousand millions [十亿], which is the "short scale. Often called the British numbering system, the long scale was used in the U.K. until the mid-1970s, and numbers in older British documents are in long scale.
上文的"in the short scale" = "俺这个billion是十亿不是万亿"。英国银老烦银了: 1几尼=1镑1先令，1镑=4克朗，1克朗=2.5弗罗林，1弗罗林=2先令，1先令=12便士，1便士=4法新。
Atoms are small enough that attempting to predict their behavior using classical physics – as if they were billiard balls, for example – gives noticeably incorrect predictions due to quantum effects. Through the development of physics, atomic models have incorporated quantum principles to better explain and predict the behavior.
原子很小，如果试图用经典物理学来预测它们的行为——比如说，就好像它们是台球一样——由于量子效应，会给出明显错误的预测。通过物理学的发展，原子模型结合了量子原理，以更好地解释和预测行为。
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and typically a similar number of neutrons. Protons and neutrons are called nucleons. More than 99.94% of an atom's mass is in the nucleus. The protons have a positive electric charge, the electrons have a negative electric charge, and the neutrons have no electric charge. If the number of protons and electrons are equal, that atom is electrically neutral. If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively, and it is called an ion.
每个原子都由一个原子核和一个或多个被原子核束缚的电子组成。原子核由一个或多个质子和数量相似的中子组成。质子和中子被称为核子。原子质量的99.94%以上在原子核中。质子带正电荷，电子带负电荷，中子不带电荷。如果质子和电子的数量相等，则该原子是电中性的。如果一个原子的电子比质子多或少，那么它就分别带有负电荷或正电荷，称为离子。
The electrons of an atom are attracted to the protons in an atomic nucleus by this electromagnetic force. The protons and neutrons in the nucleus are attracted to each other by a different force, the nuclear force, which is usually stronger than the electromagnetic force repelling the positively charged protons from one another. Under certain circumstances, the repelling electromagnetic force becomes stronger than the nuclear force, and nucleons can be ejected from the nucleus, leaving behind a different element: nuclear decay resulting in nuclear transmutation.
原子的电子被这种电磁力吸引到原子核中的质子上。原子核中的质子和中子被一种不同的力相互吸引，即核力，它通常比电磁力更强，电磁力将带正电的质子相互排斥。在某些情况下，排斥电磁力比核力更强，核子可以从原子核中弹出，留下不同的元素：核衰变导致核嬗变。核嬗变是一种化学元素转化成另外一种元素，或一种化学元素的某种同位素转化为另一种同位素的过程。
The number of protons in the nucleus defines to what chemical element the atom belongs: for example, all copper atoms contain 29 protons. The number of neutrons defines the isotope of the element. The number of electrons influences the magnetic properties of an atom. Atoms can attach to one or more other atoms by chemical bonds to form chemical compounds such as molecules. The ability of atoms to associate and dissociate is responsible for most of the physical changes observed in nature and is the subject of the discipline of chemistry.
原子核中质子的数量决定了原子所属的化学元素：例如，所有铜原子都含有29个质子。中子的数量决定了元素的同位素。电子的数量影响原子的磁性。原子可以通过化学键与一个或多个其他原子结合，形成分子等化合物。原子的结合和解离能力是自然界观察到的大多数物理变化的原因，也是化学学科的主题。
所有的氢原子都含1个质子(氢可以是总称)。氕piē, 元素符号H，含0个中子，最常见(氢也可以是它)。氘dāo也叫重氢，元素符号一般为D或2H，含1个中子 …… 可以一直排到氢-7，它含6个中子。氢燃料电池是将氢气和氧气的化学能直接转换成电能的发电装置。其基本原理是电解水的逆反应。9家燃料电池企业配套重卡展开示范运营-氢燃料电池--国际氢能网