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Objectives

Learn about the differences between compounds and elements, parts of chemical formulas, and why chemical bonding occurs. Explore the stability in bonding and the types of bonds formed in chemistry.

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Objectives

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  1. Objectives • Describe how a compound differs from an element. • Identify parts of a chemical formula. • Explain why chemical bonding occurs. • CLE 3202.1.7 Construct chemical formulas for common compounds.

  2. Chemical Bonds

  3. Stability in Bonding A. Some elements combine chemically and no longer have the same properties they did before forming a compound

  4. Stability in Bonding B. Compounds make up most of matter because arrangements of electrons in most atoms make them chemically unstable.

  5. Stability in Bonding C. Stable atoms must have 8 electrons. Atoms share, gain or lose electrons to become more stable.

  6. Stability in Bonding D. A chemical bond forms when an atom gains, loses or shares electrons.

  7. Stability in Bonding E. A chemical formula tells what elements make up a compound and the ratio of the atoms of those elements.

  8. Stability in Bonding 1. A(n) chemical formula is composed of symbols and subscripts indicating the number of atoms of an element in a compound

  9. Stability in Bonding Iron oxide water sulfuric acid (rust) (battery acid) Fe2O3 H2O H2SO4 2:3 2:1 2:1:4 HC2H3O2 vinegar 1:2:3:2 acetic acid

  10. Stability in Bonding F. An atom is chemically stable if its outer energy level is completely filled with electrons. Noble (inert gases) gases are chemically stable. • He – 2 atoms • Most others – 8

  11. Stability in Bonding G. Atoms form compounds when the compound is more stable than the separate atoms.

  12. Stability in Bonding 1. Noble gases are more chemically stable than other elements because they have a complete outer energy level.

  13. Stability in Bonding 2. Elements that do not have full outer energy levels are more stable in compounds.

  14. Stability in Bonding 3. Atoms can lose, gain, or share electrons to get a stable outer energy level.

  15. Stability in Bonding 4. A chemical bond is the force that holds atoms together in a compound.

  16. Why do elements form compounds? To become more chemically stable by getting a complete outer energy level

  17. Objectives • Describe how a compound differs from an element. • Identify parts of a chemical formula. • Explain why chemical bonding occurs. • CLE 3202.1.7 Construct chemical formulas for common compounds.

  18. Types of Bonds 19-2

  19. Objectives • Given a periodic table, determine the oxidation numbers. • Distinguish between ionic and covalent bonds. • CLE 3202.1.7 Construct chemical formulas for common compounds. • CLE 3202.1.6 Distinguish between common compounds formed by ionic and covalent bonds.

  20. Types of Bonds • Ionic Bonds 1. Atoms can gain or lose electrons in the outer energy level.

  21. Ionic Bonds 2. When the number of electrons is different from the number of protons, the atom has an electrical charge.

  22. Ionic Bonds 3. The name of this charged particle is ion.

  23. Ionic Bonds • When an atom loses an electron, it becomes a positively charged ion; a. A superscript indicates the charge.

  24. Ionic Bond 5. When an atom gains an electron, it becomes a negatively charged ion. Na+ Cl-

  25. Types of Bonds B. An ionic compound is held together by the ionic bond – the force of attraction between opposite charges of the ions.

  26. Ionic Bond-Transfer

  27. Ionic Bond-Transfer

  28. Ionic Bond 1. The result of this bond is a(n) neutral compound.

  29. Ionic Bond 2. The sum of the charges on the ions is zero.

  30. Types of Bonds C. Molecules are neutral particles formed as a result of sharing electrons.

  31. Covalent Bond 1. A covalent bond is the force of attraction between atoms sharing electrons.

  32. Covalent Bond 2. Atoms can form double or triple bonds depending on whether they share two or three pairs of electrons.

  33. Covalent Bond 3. The covalent compound has a complete outer energy level.

  34. Triple Bonds-Nitrogen

  35. Covalent Bond Each hydrogen atom shares one of its electrons with the oxygen atom. All atoms have a complete outer energy level. The entire molecule is neutral

  36. Covalent Bond 4. Electrons shared in a molecule are held more closely to the atoms with the larger nucleus.

  37. Covalent Bond 5. A polar molecule has one end that is slightly negative and one end that is slightly positive, although the overall morecule is neutral.

  38. Polar Covalent Bond Water

  39. Covalent Bone 6. In a(n) nonpolar molecule, electrons are shared equally.

  40. Non-polar Covalent Bond Methane

  41. What two types of atomic bonds form and how do they differ? Ionic bonds form when atoms lose or gain electrons; covalent bonds form when atoms share electrons.

  42. Objectives • Given a periodic table, determine the oxidation numbers. • Distinguish between ionic and covalent bonds. • CLE 3202.1.7 Construct chemical formulas for common compounds. • CLE 3202.1.6 Distinguish between common compounds formed by ionic and covalent bonds.

  43. Writing Formulas and Naming Compounds 19-3

  44. Writing Formulas & Naming Compounds • Chemists use symbols from the periodic table to write formulas for compounds.

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