Atoms and atomic theory
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The periodic table is arranged in such a way that elements in the same vertical column have similar characteristics. Therefore, it is often useful to refer to all the elements in a given column as a group or family. Each group has a number, and some have a group name. For English in chemistry 1 – 2017 TS. Nguyễn Tuyết Phương – TS. Trần Thu Phương 5 example, the last column on the right is group 18, and the elements in this column are called noble gases. Main- group elements are those in groups 1, 2, and 13 to 18. When main-group metal atoms in groups 1 and 2 form ions, they lose the same number of electrons as their group number. Whereas when nonmetal atoms form ions, they gain electrons. Most of the elements are classified as metals, which means they have the following characteristics. - Metals have a shiny metallic luster. - Metals conduct heat well and in the solid form conduct electric currents. - Metals are malleable, which means they are capable of being extended or shaped by the blows of a hammer. (For example, gold, Au, can be hammered into very thin sheets without breaking.) There is more variation in the characteristics of the nonmetal elements. Some of them are gases at room temperature and pressure, some are solids, and one is a liquid. They have different colors and different textures. The definitive quality shared by all nonmetals is that they do not have the characteristics mentioned above for metals. For example, sulfur is a dull yellow solid that does not conduct heat or electric currents well and is not malleable. It shatters into pieces when hit with a hammer. A few of the elements have some but not all of the characteristics of metals. These elements are classified as tải về 0.52 Mb. Chia sẻ với bạn bè của bạn:
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