化学元素_综合百科

化学元素(element, chemical)

构成所有物质的基本材料，已知的化学元素约有115种，构成元素最小的单位是原子。一个元素的所有原子在原子核的电荷（即质子数）和电子数（参阅atomic number）是相同的，但如果它们的中子数不一样，质量（原子量）就可能不同（参阅isotope）。每一种元素有一或两个字母的化学符号。元素能互相化合形成多种复杂的化合物。原子序数大於83（铋）的所有元素和一些较轻元素的同位素都是不稳定、放射性的元素。超铀元素（原子序数大於92）是在1940年以後被发现，以中子或快速运动的带电粒子轰击一种元素而产生的。已知的化学元素中有11种是气体，2种是液体，其余都是固体。地壳中含量最丰富的元素是氧（46%）、矽（26%）、铝（8%）、铁（5%）。

English version：

element, chemical

One of the 115 presently known kinds of substances that constitute all matter at and above the level of atoms, the smallest unit of any element. All atoms of an element are identical in nuclear charge (number of protons) and number of electrons (see atomic number), but their mass (atomic weight) may differ if they have different numbers of neutrons (see isotope). Each element has a one- or two-letter chemical symbol. Elements combine to form a wide variety of compounds. All elements with atomic numbers greater than 83 (bismuth), and some isotopes of lighter elements, are unstable and radioactive (see radioactivity). The transuranium elements, with atomic numbers greater than 92 (see uranium), artificially created by bombardment of other elements with neutrons or other heavy particles, have been discovered since 1940. The most common elements (by weight) in the earth's crust are oxygen, 49%; silicon, 26%; aluminum, 8%; and iron, 5%. Of the known elements, 11 (hydrogen, nitrogen, oxygen, fluorine, chlorine, and the six noble gases) are gases, two (bromine and mercury) are liquids (two more, cesium and gallium, melt at about or just above room temperature), and the rest are solid under ordinary conditions. See also periodic table.

参考文章