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. The periodic table is an arrangement of the elements in order of increasing atomic number. 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. As you might expect, elements colored in gold that lie along the diagonal line exhibit properties intermediate between metals and nonmetals they are called semimetals. The heavy orange zigzag line running diagonally from the upper left to the lower right through groups 13–16 in 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). The semimetals lie along a diagonal line separating the metals and nonmetals. The metals are on the bottom left in the periodic table, and the nonmetals are at the top right. Remember that all the alkali metals react vigorously with halogens to produce salts, as the halogens needs one electron to complete its octet and alkali metals can readily lose electrons to have an oxidation state of $ +1.\) The Periodic Table Showing the Elements in Order of Increasing Z Cesium is second from the bottom of this group, with six electron shells, so it fits all the characteristics of a reactive atom, therefore making it the most reactive element. Down to the Francium the reactivity must be slightly decreased due to the heavy nuclei.Īlkali metals (situated far away from transitional metals and noble gases) are the most reactive element group. There is no relation of radioactivity and tendency to forming compounds. Due to that heavy nuclei the interactions between the nucleus and the electron is more and hence it requires high energy to remove an electron from the outermost shell. But it is not the case, Francium has a heavier nucleus than Cesium and it causes radioactivity. $Īs we know that reactivity increases down the group, so, you must be thinking that Francium is looking more reactive. They tend to donate their electrons in reactions and have an oxidation state of $ +1. Alkali metals are among the most reactive metals in the periodic table and this is due to their larger atomic radii and low ionization energies. Reactivity of elements increases down the group. They easily react with water to form an alkaline metal hydroxide solution and hydrogen. The elements are generally soft, reactive metals with low melting points. For example, Noble gases have low reactivity because they have full electron shells. Hint :We know that the number of electrons in the outermost shell of an atom and its tendency to lose electrons determines its reactivity.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |