Elements and Compounds


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Elements and Compounds

  1. 1. Elements and Compounds A Mr. Mularella Presentation
  2. 2. The 4 Ancient Elements Earth Fire Air Water
  3. 3. Elements <ul><li>There are currently 118 elements that have been identified though only 88 of them are naturally occurring. </li></ul>
  4. 4. Elements in the Universe <ul><li>In our universe, hydrogen makes up 75% of all matter! </li></ul><ul><li>Helium makes up about 20% with oxygen being the 3 rd most abundant element. </li></ul><ul><li>All of the other elements are relatively rare in the universe. </li></ul>
  5. 5. Elements in the Earth <ul><li>In the Earth’s crust, oxygen is the most abundant element (46.6%). </li></ul><ul><li>Silicon is the second most abundant element (27.7%). </li></ul><ul><li>Aluminum (8.1%), iron (5.0%), calcium (3.6%), sodium (2.8%), potassium (2.6%). and magnesium (2.1%) complete the list of elements that account for approximately 98.5% of the total mass of the earth's crust. </li></ul>
  6. 6. Elements <ul><li>Elements are a pure substance. </li></ul><ul><ul><li>Made of only one kind of material, has definite properties, and is the same all throughout. </li></ul></ul><ul><li>Elements are the simplest pure substance. </li></ul><ul><ul><li>They cannot be broken down into simpler substances without losing their identity. </li></ul></ul>
  7. 7. Elements and Atoms <ul><li>The smallest particle of an element that has the properties of that element is called an atom . </li></ul><ul><li>Atoms: the building blocks of matter. </li></ul><ul><li>Atoms of the same element are alike; atoms of different elements are different. </li></ul>
  8. 8. Chemical Symbols <ul><li>Shorthand way of representing the elements. </li></ul><ul><li>Usually one or two letters. </li></ul><ul><li>Usually taken from the name of the element. </li></ul><ul><ul><li>Carbon-C, Calcium-Ca, Hydrogen-H, Iodine-I, Oxygen-O, Chlorine-Cl </li></ul></ul>
  9. 9. Chemical Symbols <ul><li>Some symbols come from their Latin name: </li></ul><ul><ul><li>Gold-Au--aurum </li></ul></ul><ul><ul><li>Silver-Ag--argentum </li></ul></ul><ul><ul><li>Iron-Fe--Ferrum </li></ul></ul><ul><ul><li>Mercury-Hg--hydrogyrum </li></ul></ul>
  10. 10. Compounds <ul><li>Pure substances made up of more than one element. </li></ul><ul><li>2 or more elements chemically combined. </li></ul><ul><li>Ex: H 2 O, NaCl, C 6 H 12 O 6 , CO 2 </li></ul><ul><li>Unlike elements, compounds can be broken down to simpler substances. </li></ul><ul><li>This can happen through a chemical reaction. </li></ul>
  11. 11. Compounds <ul><li>The properties of the elements that make up a compound are often quite different from the properties of the compound itself. </li></ul><ul><ul><li>Sodium-Na--highly reactive metal </li></ul></ul><ul><ul><li>Chlorine-Cl--poisonous gas </li></ul></ul><ul><ul><li>Sodium Chloride-NaCl--table salt </li></ul></ul>
  12. 12. Molecules <ul><li>Compounds are made of molecules. </li></ul><ul><ul><li>A molecule is 2 or more atoms chemically bonded. </li></ul></ul><ul><ul><li>Water-2 atoms of hydrogen and one atom of oxygen-together they form one molecule of H 2 O. </li></ul></ul><ul><li>A molecule is the smallest particle of a compound that has all the properties of that compound. </li></ul><ul><li>Just as all atoms of a certain element are alike, all molecules of a certain compound are alike. </li></ul>
  13. 13. Chemical Formulas <ul><li>A shorthand way of representing compounds. </li></ul><ul><li>If chemical symbols are the “letters,” these are the “words.” </li></ul><ul><li>Ex: NH 3 - ammonia, C 3 H 7 OH - rubbing alcohol </li></ul><ul><li>Sometimes, the formula represents a molecule of a single element. </li></ul><ul><li>These are called diatomic molecules. This is how that element is naturally found. </li></ul><ul><ul><li>O 2 -Oxygen H 2 -Hydrogen Cl 2 -Chlorine </li></ul></ul>
  14. 14. Chemical Formulas <ul><li>Subscripts are small numbers used in chemical formulas. </li></ul><ul><li>They are placed to the lower RIGHT of the chemical symbols. </li></ul><ul><li>Represent # of atoms of an element in a compound. </li></ul><ul><li>CO 2 = 1 atom of carbon and 2 atoms of oxygen. </li></ul><ul><li>H 2 SO 4 = 2 atoms of hydrogen, 1 atom of sulfur and 4 atoms of oxygen </li></ul>