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Chapter 6 Meet The Elements 6.1 Symbols for the Elements Read p 192-197 Chemical Symbols and Formulas - answer questions on p. 197 1-6ab Know how to complete chart on page 196 Know the symbols for the first 20 elements of the periodic table on p. 562 6.2 Elements on The Planet Earth Read p. 198-200 Questions: 1. What are the 4 main gases found in our atmosphere? 2. Why is photosynthesis vital for life on Earth? 3. What is the hydrosphere? 4. List one element and 4 compounds found in our hydrosphere? 5. What is the importance of dissolved 02 and CO2 in our hydrosphere? 6. List the four most common elements in the Earth’s crust. 7. Oxygen is the most abundant element in the Earth’s crust, yet the Earth’s crust is solid. How is this possible? 8. Only a few metallic elements exist in nature in an uncombined state. List these elements. Different Kinds of Elements Read p. 203-204 Questions: 1. There are two main categories of elements and one category which lies in between these. List these three categories of elements and give the general properties of each group. 2. a) What does the term “malleable” mean? 3. b) What does the term “ductile” mean? 4. List 6 common metals and 6 common non-metals. 5. Why did it take so long for people to start using aluminum, even though it is the most abundant metal in the Earth’s crust? 6.3 Metallurgy Metallurgy is the study of metals- their properties, structure, refining from ores, alloys, and formation of finished products. There are three main processes in metallurgy: extraction, modification, and alloying. Rarely are metals found lying around in chunks in nature. Instead, they are almost mixed with other materials in compounds. This mixture, buried in rock is called a mineral and if there is enough of the mineral present, to make it worthwhile to mine, the rock is called an ore. Extraction - is the mechanical and chemical processes used to remove metals from the minerals and ores and that contain them. There are 2 main components of extraction: 1. Concentration – removing as much rock as possible, so that the remaining mixture contains as much of the mineral as possible. This involves crushing and separating the ore from the waste rock mixed with it. 2. Decomposition – is a process of breaking down the mineral compound by a chemical change in order to obtain the metal in a nearly pure form. This is often referred to as smelting. Smelting involves mixing the concentrated mineral with chemical and adding heat or electricity (electrolysis). Modification - Altering the properties of a pure metal, without using a chemical change. An example would heating and beating metal to make it tougher and harder. This process is know n as tempering. Alloying – mixing metals with one or more metals to produce a new metal with desirable qualities. Examples: bronze (copper + tin) yellow gold (gold + copper) pewter (tin + lead + copper) stainless steel (iron + carbon + nickel + chromium) 6.4 Families of Elements Chemical Family – is a term used to describe a group of related elements. For example, copper, silver and gold all belong to the same chemical family. These metals are often referred to as the coinage metals, even though few countries use them to make new coins today. Complete Page 216 Science Inquiry Activity – Patterns of Properties in a Chemical Family The Periodic Table The Periodic Table – is a table in which the elements are organised in rows or columns, according to their atomic number and their patterns of similar properties. Atomic number – is the number of protons in the nucleus of an atom. This number is ABOVE the element’s symbol. An element’s position in the periodic table is determined by it’s atomic number. The atomic number (number of protons) makes each element unique from the others. Vertical columns are called GROUPS. Families of elements with similar properties, such as the coinage metals are located in the same group. Horizontal rows are called PERIODS. The atomic number of elements increases as you move from left to right across the table, starting with hydrogen (H) which has an atomic number of 1. Atomic Mass – is the mass of an average atom of an element. It also equal the total number of protons and neutron in the nucleus of an atom. Atomic Structure Atoms – an atom is the smallest unit of matter that can take place in a chemical change. The word comes from the Greek word Atomos which means indivisible. All matter is made up of atoms. Atoms are composed of protons, neutrons and electrons. Protons have a positive electrical charge. Neutrons have a neutral charge. Electrons have a negative electrical charge. Atoms have a nucleus which contain protons and neutrons and the electrons form a cloud around the nucleus. These electrons move Bohr-Rutherford model of atomic structure – (not the last word on atomic structure) can be called the first “modern view” of an atom. It compares the nucleus of an atom to the sun, and the electrons to the planets, which remain in their orbits revolving around the nucleus. These orbits are called “electron shells”