General Chemistry: The Structure of Matter PDF

MED-102 General Chemistry The Structure of Matter  Learning Objectives (LOBs) Describe the arrangement of the Periodic Table Describe the main properties of metals, non-metals, and metalloids Identify the names, positions, and main properties of selected groups in the Periodic Table ...

MED-102 General Chemistry The Structure of Matter  Learning Objectives (LOBs) Describe the arrangement of the Periodic Table Describe the main properties of metals, non-metals, and metalloids Identify the names, positions, and main properties of selected groups in the Periodic Table  What is Chemistry? Chemistry is the science that describes matter and the different transformations of matter from one form to another  Chemical Elements An element is the most fundamental form of matter and it cannot be broken down by chemical methods into simpler substances  The Periodic Table The Periodic Table is a logical arrangement of the known elements in terms of their chemical properties  The Periodic Table – Revision Slide Rows are called Periods – they contain chemically unrelated elements Columns are called Groups – they contain chemically similar elements Soft metals appear on the left-hand side of the Periodic Table – first two columns Traditional metals appear in the middle section (yellow) – Transition Metals More metals appear in green Aqua-blue diagonal section contains semimetals (metalloids) Non-metals appear in light blue, mauve and purple colours – right-hand side of the Periodic Table Groups 1A, 2A (left side) and 3A to 8A (right side) are called the Main Group elements Groups 1B to 8B (middle - yellow) are the Transition Metals  Element categories Metals: shiny, conduct heat and electricity very well. All except Mercury (Hg) are solids. Malleable (pounded into sheets) and ductile (drawn into wires). Non-metals: gases, liquids, or solids. Brittle solids (shatter easily) and are poor conductors of heat and electricity. Metalloids: properties are intermediate between metals and non-metals.  Polyatomic Elements Most elements are monatomic, made up of single atoms. There are, however, seven diatomic elements and some polyatomic. Diatomic elements: H2 N2 O2 {F2 Cl2 Br2 I2} Triatomic element: O3 (ozone) Polyatomic elements: P4 (red phosphorus) S8 (orthorhombic sulphur)  Group 1A – Alkali Metals React violently with water, some catching on fire due to the production of hydrogen gas and large amounts of heat given off  Group 1A – Alkali Metals – Revision Slide WATCH: https://www.youtube.com/watch?v=6ZY6d6jrq-0 Hydrogen (H) is in Group 1A, but it is not considered an alkali metal. When alkali metals are placed in water, they float around as their density is less than that of water. The chemical reaction with water releases hydrogen gas, which is combustible and often catches on fire. The chemical reaction with water is exothermic (releases heat) and produces an alkaline (basic) solution. The metal actually disappears during the reaction, and seems to dissolve fully in water. The chemical reactivity of the metals increases as we go down the group. While lithium (Li) just floats around without catching on fire, sodium (Na) does catch on fire. Cesium (Cs) will actually explode in the water as it is much more reactive. Francium (Fr), the lowest alkali metal, is actually radioactive and is not often used in chemistry labs.  Group 2A – Alkaline Earth Metals Also react with water producing hydrogen gas and an alkaline solution, but less reactive than Alkali Metals.  Group 2A – Alkaline Earth Metals – Revision Slide WATCH: https://www.youtube.com/watch?v=dUbjn3ix3ds Alkaline-earth metals are called so because some of them are found in rocks in the Earth’s mantle (solid layer). The reactivity of alkaline-earth metals increases as we go down the group. Alkaline-earth metals react with water to produce hydrogen gas and an alkaline solution. Alkaline-earth metals are less reactive than alkali metals. Radium (Ra) is a radioactive metal and is not used often in chemistry labs. Magnesium (Mg) and Calcium (Ca) are important elements for maintaining good health. 5-Minute Break  Group 6A - Chalcogens Chalco (χαλκός) means copper. Copper ores (rocks) contain copper in combination with one of these elements. Proper chemical treatment gives rise (-gen) to copper metal.  Group 7A - Halogens Halo (άλας) means salt. These elements form common salts, like NaCl, etc., in combination with a metal like Na, K, etc.  Group 7A – Halogens – Revision Slide WATCH: https://www.youtube.com/watch?v=ji_25I_q4LQ Halogens exist in nature as diatomic elements. Fluorine (F) is the most reactive halogen. Astatine (At) is radioactive and is not used often in chemistry labs. Fluorine (F) and Chlorine (Cl) are toxic gases if they are breathed in, forming acids when they react with water on the lung surface, which causes severe burns. Bromine (Br) is an orange-brown volatile liquid. Iodine (I) is a black solid, which turns to a purple vapour when heated. They react chemically with alkali metals to form salts, like sodium chloride (NaCl), or common table salt.  Group 8A – Noble Gases Also known as inert gases, or rare gases, they are gases that are very unreactive chemically. Their main source is the atmosphere.  Group 8A – Noble Gases – Revision Slide WATCH: https://www.youtube.com/watch?v=9rAh9ic_l4I Helium (He) is used in balloons that rise in air. It is also used in blimps (airships). When you breath in helium gas, your voice changes and becomes very thin for a while. Neon (Ne) is used in making illuminated advertisement signs. Radon (Rn) is radioactive and is a principal cause of lung cancer. It floats upwards through the soil from the nuclear fission (breakup) of uranium found in the Earth’s mantle. It is dangerous because it is a gas and can come into contact with the lung tissue. Noble gases are also known as inert gases because they do not react chemically, except under extreme conditions. Their chemical reactivity increases down the group.  SBA Question 1 A certain element exists in gaseous form in nature. It is required by humans in the process of respiration. In which Group of the Periodic Table does this element belong? A. Alkali metals. B. Alkaline-earth metals. C. Chalcogens. D. Halogens. E. Noble gases.  SBA Question 1 A certain element exists in gaseous form in nature. It is required by humans in the process of respiration. In which Group of the Periodic Table does this element belong? A. Alkali metals. B. Alkaline-earth metals. C. Chalcogens. D. Halogens. E. Noble gases. It is clear that the element is oxygen, which exists as diatomic O2. It is a chalcogen.  SBA Question 2 Which element does not exist in diatomic form? A. Fluorine. B. Hydrogen. C. Nitrogen. D. Oxygen. E. Phosphorus.  SBA Question 2 - Answer Which element does not exist in diatomic form? A. Fluorine. B. Hydrogen. C. Nitrogen. D. Oxygen. E. Phosphorus. Phosphorus is found either in tetratomic form (P4) as red phosphorus or in monatomic form (P) as white phosphorus.  SBA Question 3 An element is shiny, but breaks up into pieces when hit with a hammer. It conducts electricity under certain conditions. Which of the following could this element be? A. Aluminium. B. Bromine. C. Magnesium. D. Silicon. E. Phosphorus.  SBA Question 3 An element is shiny, but breaks up into pieces when hit with a hammer. It conducts electricity under certain conditions. Which of the following could this element be? A. Aluminium. B. Bromine. C. Magnesium. D. Silicon. E. Phosphorus. The element has properties of metals and nonmetals, so it must be a metalloid. Silicon is a well-known metalloid (semimetal).  Summary for Revision Chemistry is the science of matter and its transformations. Elements are the simplest building blocks of nature. They are collected in a logical fashion in the Periodic Table according to their chemical reactivity. The Periodic Table contains all the known elements. On Earth, elements up to Uranium can be found. Elements heavier than uranium can be produced in physics labs. The Periodic Table is arranged in rows (periods) and columns (groups). Groups contain elements that have similar chemical reactivity. Metals are usually hard, shiny and conduct heat and electricity. Non-metals can be solids, liquids, or gases. They do not normally conduct heat or electricity, and if solids, they are brittle. Metalloids (semimetals) have properties of both metals and non-metals. Alkali metals (Group 1A) are soft and react with water to form hydrogen gas and an alkaline solution. The chemical reactivity of alkali metals increases down the group. Alkaline-earth metals (Group 2A) are also soft and react with water in a manner similar to that of alkali metals. They are, however, less reactive than alkali metals. They are found in rocks in the Earth’s mantle. Chalcogens (Group 6A) are found in copper ores in the Earth’s mantle. Halogens (Group 7A) are the salt-forming elements. Salts form when halogens react with metals. Halogens are diatomic elements. Noble Gases (Group 8A) are chemically inert. They have a variety of common uses.