These individual element summary pages contain a lot of additional. When exploring the table or list views on this page, please note the links to dedicated pages for each element. (This isotope is known as “carbon-12” as will be discussed later in this chapter. PubChem is providing this periodic table page in order to help navigate abundant chemical element data available in PubChem. Antimony compounds have been known since ancient times and were powdered for use as medicine and cosmetics, often known by the Arabic name kohl. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb 2 S 3 ). Since 1961, it has been defined with regard to the most abundant isotope of carbon, atoms of which are assigned masses of exactly 12 amu. Antimony is a chemical element with the symbol Sb (from Latin stibium) and atomic number 51. The amu was originally defined based on hydrogen, the lightest element, then later in terms of oxygen. When describing the properties of tiny objects such as atoms, we use appropriately small units of measure, such as the atomic mass unit (amu) and the fundamental unit of charge (e). For example, a carbon atom weighs less than 2 × 10 - 23 g, and an electron has a charge of less than 2 × 10 - 19 C (coulomb). (credit middle: modification of work by “babyknight”/Wikimedia Commons credit right: modification of work by Paxson Woelber)Ītoms-and the protons, neutrons, and electrons that compose them-are extremely small. For a perspective about their relative sizes, consider this: If the nucleus were the size of a blueberry, the atom would be about the size of a football stadium ( Figure 2.3.1).įigure 2.3.1 If an atom could be expanded to the size of a football stadium, the nucleus would be the size of a single blueberry. The diameter of an atom is on the order of 10 - 10 m, whereas the diameter of the nucleus is roughly 10 - 15 m-about 100,000 times smaller. The nucleus contains the majority of an atom’s mass because protons and neutrons are much heavier than electrons, whereas electrons occupy almost all of an atom’s volume. It was learned that an atom contains a very small nucleus composed of positively charged protons and uncharged neutrons, surrounded by a much larger volume of space containing negatively charged electrons. The development of modern atomic theory revealed much about the inner structure of atoms.
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