![]() Semimetals exhibit properties intermediate between those of metals and nonmetals. The elements can be broadly divided into metals, nonmetals, and semimetals. Some of the groups have widely-used common names, including the alkali metals (Group 1) and the alkaline earth metals (Group 2) on the far left, and the halogens (Group 17) and the noble gases (Group 18) on the far right. Elements that exhibit similar chemistry appear in vertical columns called groups (numbered 1–18 from left to right) the seven horizontal rows are called periods. It arranges of the elements in order of increasing atomic number. The periodic table is used as a predictive tool. As expected, semimetals exhibit properties intermediate between metals and nonmetals. Most solid nonmetals are brittle, so they break into small pieces when hit with a hammer or pulled into a wire. Nonmetals can be gases (such as chlorine), liquids (such as bromine), or solids (such as iodine) at room temperature and pressure. Nonmetals, in contrast, are generally poor conductors of heat and electricity and are not lustrous. Of the metals, only mercury is a liquid at room temperature and pressure all the rest are solids. The vast majority of the known elements are metals. Metals-such as copper or gold-are good conductors of electricity and heat they can be pulled into wires because they are ductile they can be hammered or pressed into thin sheets or foils because they are malleable and most have a shiny appearance, so they are lustrous. The distinction between metals and nonmetals is one of the most fundamental in chemistry. X(g) +e X2(g) (3) (3) X ( g) + e X 2 ( g) It is the energy needed to carry out this change per mole of X X. ![]() This is more easily seen in symbol terms. Gold-colored lements that lie along the diagonal line exhibit properties intermediate between metals and nonmetals they are called semimetals. The second electron affinity is the energy required to add an electron to each ion in 1 mole of gaseous 1- ions to produce 1 mole of gaseous 2- ions. Some halides of the world are a part of molecules with covalent bonds.\) divides the elements into metals (in blue, below and to the left of the line) and nonmetals (in bronze, above and to the right of the line). Don't think that the halogens always make ionic compounds and salts. One of the best examples of a halide is sodium chloride (NaCl). When a halogen combines with another element, the resulting compound is called a halide. The elements we are talking about in this section are called halogens. Their chemical properties change just a little bit when compared to the element right above them on the table. As the atomic number increases, the atoms get bigger. As you learn more about the table, you will find this pattern true for other families. Reactivity decreases as you move down the column. Fluorine is the most reactive and combines with most elements from around the periodic table. Not all halogens react with the same intensity or enthusiasm. We've just told you how reactive the halogens are. The elements in the column on the left each have one electron that they like to donate. The elements that make up the group of halogens in row seven of the Periodic Table are Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At). You will often find them bonding with metals and elements from Group One of the periodic table. Because they are so close to being happy, they have the trait of combining with many different elements. They are all just one electron shy of having full shells. That seven-electron trait applies to all of the halogens. When you look at our descriptions of the elements fluorine and chlorine, you will see that they both have seven electrons in their outer shell. Who is in this family? The elements included are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). This column is the home of the halogen family of elements. ![]() The electron configuration in the outer shell is ns2np5 n s 2 n p 5. In the second column from the right side of the periodic table, you will find Group Seventeen (Group XVII). The halogens all have seven electrons in their outer shells. ![]()
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