Chem Class - March 17, 2010

     THE CHEMICAL FAMILIES

     The vertical columns in the periodic table are known as groups or chemical families. There are five groups: Alkali Metals, Alkaline Earth Metals, Transition Metals, Halogens and Noble Gases. Hydrogen is actually in a separate group on its own. Elements in the same chemical family have similar physical and chemical properties.

     The Alkali Metals are in group 1 of the Periodic Table (points). IT includes Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium. Elements in this family are highly reactive and reactivity increases as you go down the group. These metals have only one electron in their outer shell and so, they are always ready to lose that one electron in ionic bonding with other elements. They react readily with non-metals such as oxygen and water, and usually have lower densities than other metals. They also are malleable, ductile, good conductors of heat and electricity and have low melting points, all of which are below 200 °C. Finally, alkali metals are soft and can actually be cut with a knife.

     Elements in the second column are part of the Alkaline Earth Metal family. This includes Beryllium, Magnesium, Calcium, Strontium, Barium and Radium. They have two electrons in their outer shell and have low electronegativities. They are also less reactive than Alkali Metals but they will burn in air if heated. They will also react with water. They are all metals with a shiny, silvery white colour.

    

     The Transition Metals are the 38 elements in groups 3-12 of the periodic table. They are very hard, have high melting and boiling points, low ionization energies, high electrical conductivity and are malleable, which means that they are able to be shaped and bent.

     The Halogens are in group 17 of the periodic table. They are Fluorine, Chlorine, Bromine, Iodine, and Astatine. They are highly reactive non-metals with strong and unpleasant odours. In addition, they will burn flesh and do not react well with water. Fluorine and chlorine are gases at room temperature, Bromine is a liquid and Iodine and Astatine are solids.

     The last family is the Noble Gases, found in group 18 of the Periodic Table. They include Helium, Neon, Argon, Krypton, Xenon and Radon. The Noble Gases are the most stable and unreactive elements in the periodic table. They are colourless, odourless gases at room temperature. They also have high ionization energies and low boiling points.