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Scientist: Per: Date: ____________________ _________ _________ UNIT 1: ATOMS AND ELEMENTS #7 Reading: Groups of the Periodic Table Alkali Metals (Group 1A) The Alkali metals, found in group 1A of the periodic table are extremely reactive metals. The word “alkali” or “alkaline” refers the chemical property of these elements to react with other elements to form a special kind of chemical compound called a base (we will learn about these later… but you may have heard of acids and bases, or perhaps alkaline batteries). Because the Alkali Metals are so chemically reactive, these elements do not exist in nature in their pure form. Pure samples of these elements must be produced through chemical reactions. As with all metals, the alkali metals are malleable, ductile, and are good conductors of heat and electricity. The Alkali Metals are softer than most other metals, and can easily be cut with a butter knife. They have low densities and will float on water. Cesium and francium are the most reactive elements in this group. Alkali metals can explode if they are exposed to water. They also react to the oxygen in the air, forming a gray oxide layer on the metal’s surface. Alkaline Earth Metals (Group 2A) The Alkaline Earth Metals are metallic elements found in the second group of the periodic table. They are shiny, and have a silvery-white appearance. The Alkaline Earth Metals are also very reactive, but slightly less so than the Alkali Metals mentioned above. Because of their reactivity, the Alkaline Earth Metals are not found in nature in their pure elemental form… they are always bonded to other elements in various rocks and minerals. For example, calcium is the fifth most abundant element in the earth’s crust, but is only found in minerals such as chalk, limestone, and gypsum. Transition Metals (“B” Groups) The 38 elements in the “B Groups” of the periodic table are called "Transition Metals". As with all metals, the transition elements are both ductile and malleable, and conduct electricity and heat. While the Alkali Metals (1A) and Alkaline Earth Metals (2A) both demonstrate predictable patterns in their chemical behavior based on their group, the Transition Metals tend to be more complex and a little more unpredictable. They also tend to be much more stable than their counterparts in Groups 1A and 2A, and pure samples of many transition metals exist in nature. Familiar metals such as iron, nickel, chromium, and titanium are known for their strength, shine, and stability. The precious metals in Group 11 (1B) include copper, silver, and gold, used for jewelry and for making coins. In addition, three Transition Metals - iron, cobalt, and nickel - are the only elements known to produce a magnetic field. Halogens (Group 7A) The halogens are five non-metallic elements found in Group 7A of the periodic table. The term "halogen" means "salt-former" and compounds containing halogens are called "salts". Table salt (NaCl) is just one example of a chemical “salt” but many other chemical compounds are called salts as well, such as magnesium bromide (MgBr2), aluminum fluoride (AlF3), and potassium chloride (KCl). The halogens represent all three states of matter at room temperature: fluorine and chlorine are both gases, bromine is a liquid, and iodine is a solid. The halogens are extremely reactive; they are the most reactive nonmetals. Fluorine, at the top of the group is particularly ferocious and is often considered the most reactive element on the Periodic Table. A balloon filled with fluorine gas is so volatile it can be ignited with the flash of a camera and hydrofluoric acid (containing fluorine) is exceptionally dangerous. The halogens are arguably the most important group on the Periodic Table when discussing manufacturing and industry. Fluorine is used to help break chemical compounds down and to isolate elements. Chlorine is used as a bleaching agent to make materials such as paper turn white. Various chemical compounds containing chlorine are used to kill bacteria and microorganisms in drinking water and also as a powerful insecticide in the agricultural industry. A halogen light bulb contains small amounts of iodine or bromine, which allows the light bulb to operate at higher temperatures than a standard light bulb. Noble Gases (Group 8A) As the name suggests, all of the elements in Group 8A are gases. In addition, the Noble Gases are the most stable – that is, nonreactive elements on the Periodic Table. The noble gases are almost never involved in chemical reactions. Another word for nonreactive is “inert.” Because the Noble Gases are invisible and do not react, it took a long time to discover them. Helium, now used in party balloons, was discovered in 1895… over 100 years after the more reactive gases oxygen, chlorine, and nitrogen were discovered in the 1770s. Passing an electric current through neon will bring out its familiar glow. The other Noble Gases, deliver similar results as well. Check for Understanding 1) The most reactive metals on the Periodic Table are in which group? ___________________ 2) What about nonmetals? Which is the most reactive nonmetal group?________________ 3) Where are the most stable elements on the Periodic Table? _____________________________ 4) Can we find pure sodium metal in nature? Why or why not? __________________________ _________________________________________________________________________________________________ 5) Can we find pure argon in nature? Why or why not? ___________________________________ _________________________________________________________________________________________________ 6) What is the most reactive nonmetal? _______________________________________ 7) What is the most reactive metal? _______________________________________