Chapter 2 Bonds and Compounds w-clips

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Chapter 2 Bonds and Compounds w-clips

  1. 1. Chemical Interactions <ul><li>Chapter 2: </li></ul><ul><li>Chemical Bonds </li></ul><ul><li>and Compounds </li></ul>
  2. 2. Section 2.1 Elements Combine to Form Compounds
  3. 3. Compounds have different properties from the elements that make them. <ul><li>Compound: a combination of two or more elements. </li></ul><ul><ul><li>Atoms held together by chemical bonds. </li></ul></ul><ul><ul><li>Properties of compound very different than those of the elements it is made from. </li></ul></ul><ul><li>Mixture: combination of two or more elements. </li></ul><ul><ul><li>Atoms NOT held together by chemical bonds. </li></ul></ul><ul><ul><li>Atoms maintain their individual properties. </li></ul></ul>
  4. 4. Atoms combine in predictable numbers. <ul><li>Compounds have a definite composition. </li></ul><ul><ul><li>N 2 O not the same as NO or N 2 O 2 </li></ul></ul><ul><ul><ul><li>All three are different compounds with different properties. </li></ul></ul></ul><ul><ul><li>Specific ratio of atoms. </li></ul></ul><ul><ul><li>Held together by chemical bonds. </li></ul></ul>
  5. 5. Continued – page 43 <ul><li>A chemical compound is represented by a chemical formula. </li></ul><ul><ul><li>Each elements has an alphabetic symbol (first one capital, all others lower case). </li></ul></ul><ul><ul><li>Subscripts used to show the ratio of the elements. </li></ul></ul><ul><ul><li>Example: CO 2 means 1 atom of Carbon and 2 atoms of oxygen. </li></ul></ul><ul><ul><ul><li>Atomic Ratio = 1:2 </li></ul></ul></ul>
  6. 6. Page 44
  7. 7. Section 2.2 Chemical Bonds Hold Compounds Together
  8. 8. Chemical bonds between atoms involve electrons. <ul><li>Chemical bonds are the “glue” that hold atoms in compounds. </li></ul><ul><li>A chemical bond is the result of interactions between the electron cloud of two or more atoms. </li></ul><ul><ul><li>Atoms try to fill their outer ring of eight. </li></ul></ul>
  9. 9. Atoms can transfer electrons. <ul><li>Ions are formed when atoms gain or lose electrons. </li></ul><ul><li>An ionic bond forms when one atom loses an electron, and another atom picks up that electron, forming a negative and positive ion pair. </li></ul><ul><ul><li>Gain 1 electron = negative 1 charge </li></ul></ul><ul><ul><li>Lose 1 electron = positive 1 charge </li></ul></ul>
  10. 10. Page 48 Sodium has one election in its outer ring, chlorine has 7. If Sodium give up 1 and chlorine accepts 1, the result is two completed outer rings. Everyone is happy 
  11. 11. Continued – Page 49 <ul><li>Ionic bonds produce large crystal networks of atoms. </li></ul><ul><ul><li>The attraction between the + and – ions acts in all directions. </li></ul></ul><ul><ul><li>In an ionic compound, + ions are attracted to all – ions, and – ions to all + ions. </li></ul></ul>
  12. 12. Page 49 <ul><li>Positive ion + negative ion with the suffix –ide. </li></ul><ul><ul><ul><li>Lithium + chlorine = Lithium Chloride </li></ul></ul></ul>Can you name these ionic compounds? Naming Ionic Compounds
  13. 13. Atoms can share electrons. <ul><li>Atoms that share a pair of electrons have what is called a covalent bond . </li></ul><ul><li>Atoms fill their outer rings to 8. </li></ul><ul><li>Covalent bonds can form on like or different elements. </li></ul><ul><li>In some cases, two atoms can form as many as four covalent bonds. </li></ul>
  14. 14. Continued – page 51 <ul><li>A molecule is a group of atoms held together by covalent bonds. </li></ul><ul><ul><li>Molecules have no electrical charge. </li></ul></ul><ul><li>When electrons stay much closer to one nucleus than the other, this is a polar covalent bond . </li></ul>
  15. 15. Page 51 Nonpolar Compound Polar Compound
  16. 16. Chemical bonds give all materials their structures. <ul><li>The shape of the crystal formed by an ionic compound depends on the ratio, shapes, and size of the ions. </li></ul><ul><li>Covalent compounds do not form crystals, they form individual molecules. </li></ul>
  17. 17. Continued – page 54 <ul><li>Molecules have characteristic shapes, or molecular structures. </li></ul><ul><ul><li>Molecular structure affects many properties of the compounds. </li></ul></ul>Chemically altered protein molecule.
  18. 18. Page 52
  19. 19. Section 2.3 Substances’ Properties depend on Their Bonds.
  20. 20. Metals have unique bonds. <ul><li>Metal atoms share electrons in all directions with other metal atoms in a type of bond called a metallic bond . </li></ul><ul><li>Electrons in a metal are shared by many metal atoms. </li></ul><ul><li>Properties of metals are determined by the mobility of the electrons in a metallic bond. </li></ul><ul><ul><li>Properties include: conductivity, ductility, an malleability. </li></ul></ul>
  21. 21. Page 57
  22. 22. Ionic and Covalent bonds give compounds certain Properties. <ul><li>Ionic compounds : </li></ul><ul><li>Ions are tightly located into place in the structure of a crystal. </li></ul><ul><ul><li>Usually solid at room temperature. </li></ul></ul><ul><li>Ionic bonds are difficult to break. </li></ul><ul><ul><li>Usually have high melting/boiling points </li></ul></ul>
  23. 23. Continued – page 58 <ul><li>Ionic compounds also : </li></ul><ul><ul><li>Are hard and brittle. </li></ul></ul><ul><ul><li>Do not conduct electricity when a solid. </li></ul></ul><ul><ul><li>Break up into negative and positive ions when dissolved. </li></ul></ul><ul><ul><ul><li>Will conduct electric current in a solution. </li></ul></ul></ul>
  24. 24. Continued – page 58 <ul><li>The molecules of covalent compounds are not held together as tightly. </li></ul><ul><ul><li>Boiling/melting points are relatively low. </li></ul></ul><ul><ul><li>Molecules stay intact when dissolved in water. </li></ul></ul><ul><ul><li>Molecule size and shape affect properties also. </li></ul></ul><ul><ul><li>Poor conductors of electricity. </li></ul></ul>
  25. 25. Bonds can make the same element look different. <ul><li>Allotropes: different forms of the same element. </li></ul><ul><ul><li>Result from different covalent bonds. </li></ul></ul><ul><li>Carbon forms three different allotropes, all with different properties. </li></ul><ul><ul><li>Diamonds – hardest natural substance. </li></ul></ul><ul><ul><li>Graphite – soft, dark, slippery </li></ul></ul><ul><ul><li>Fullerene - large carbon-cage molecules, the most common one is C 60 -- also called a &quot;buckyball, </li></ul></ul>

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