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  1. 1. 2 Chemical Principles
  2. 2. <ul><li>Chemistry is the study of interactions between atoms and molecules. </li></ul><ul><li>The atom is the smallest unit of matter that enters into chemical reactions. </li></ul><ul><li>Atoms interact to form molecules. </li></ul>Chemistry
  3. 3. The Study of Atoms <ul><li>Atoms are composed of </li></ul><ul><li>Electrons: Negatively charged particles </li></ul><ul><li>Protons: Positively charged particles </li></ul><ul><li>Neutrons: Uncharged particles </li></ul>
  4. 4. The Study of Atoms <ul><li>Protons and neutrons are in the nucleus. </li></ul><ul><li>Electrons move around the nucleus. </li></ul>Figure 2.1
  5. 5. Chemical Elements <ul><li>Each chemical element has a different number of protons. </li></ul><ul><li>Isotopes of an element are atoms with different numbers of neutrons. Isotopes of oxygen are: </li></ul>16 8 O 17 8 O 18 8 O
  6. 6. Table 2.1
  7. 7. Electronic Configurations <ul><li>Electrons are arranged in electron shells corresponding to different energy levels. </li></ul>
  8. 8. Electronic Configurations Table 2.2 (1 of 2)
  9. 9. Electronic Configurations Table 2.2 (2 of 2)
  10. 10. How Atoms Form Molecules: Chemical Bonds <ul><li>Atoms combine to complete the outermost shell. </li></ul><ul><li>The number of missing or extra electrons in this shell is known as the valence. </li></ul>
  11. 11. How Atoms Form Molecules: Chemical Bonds <ul><li>A compound contains different kinds of atoms. H 2 O </li></ul><ul><li>The forces holding atoms in a compound are chemical bonds. </li></ul>
  12. 12. How Atoms Form Molecules: Chemical Bonds <ul><li>The number of protons and electrons is equal in an atom. </li></ul><ul><li>Ions are charged atoms that have gained or lost electrons. </li></ul>Figure 2.2a
  13. 13. Ionic Bonds <ul><li>Ionic bonds are attractions between ions of opposite charge. One atom loses electrons and another gains electrons. </li></ul>Figure 2.2b
  14. 14. Covalent Bonds <ul><li>Covalent bonds form when two atoms share one or more pairs of electrons. </li></ul>Figure 2.3a
  15. 15. Hydrogen Bonds <ul><li>Hydrogen bonds form when a hydrogen atom covalently bonded to an O or N atom in another molecule. </li></ul>Figure 2.4
  16. 16. Molecular Weight and Moles <ul><li>The sum of the atomic weights in a molecule is the molecular weight. </li></ul><ul><li>One mole of a substance is its molecular weight in grams. </li></ul>H 2 O 2H = 2  1 = 2 O = 16 MW = 18 1 mole weighs 18g
  17. 17. Chemical Reactions <ul><li>Chemical reactions involve the making or breaking of bonds between atoms. </li></ul><ul><li>A change in chemical energy occurs during a chemical reaction. </li></ul><ul><li>Endergonic reactions absorb energy. </li></ul><ul><li>Exergonic reactions release energy. </li></ul>
  18. 18. <ul><li>Occur when atoms, ions, or molecules combine to form new, larger molecules. </li></ul><ul><li>Anabolism is the synthesis of molecules in a cell. </li></ul>Synthesis Reactions A + B AB Atom, ion, or molecule A  Atom, ion, or molecule B New molecule AB Combines to form
  19. 19. <ul><li>Occur when a molecule is split into smaller molecules, ions, or atoms. </li></ul><ul><li>Catabolism is the decomposition reactions in a cell. </li></ul>Decomposition Reactions A + B AB Atom, ion, or molecule A  Atom, ion, or molecule B New molecule AB Breaks down into
  20. 20. Exchange Reactions <ul><li>Are part synthesis and part decomposition. </li></ul>NaCl + H 2 O NaOH + HCl 
  21. 21. <ul><li>Can readily go in either direction. </li></ul><ul><li>Each direction may need special conditions. </li></ul>Reversible Reactions A + B Water   AB Heat