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Chapter 11

Chapter 11. Chemical Bonding. Section 1: Objectives. Describe chemical bonding. Identify the number of valence electrons. Predict whether an atom is likely to form bonds. Combining Atoms. All substances are made up of atoms of one or more of the elements.

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Chapter 11

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  1. Chapter 11 Chemical Bonding

  2. Section 1: Objectives • Describe chemical bonding. • Identify the number of valence electrons. • Predict whether an atom is likely to form bonds.

  3. Combining Atoms • All substances are made up of atoms of one or more of the elements. • Chemical bonding: joining of atoms to form new substances • Chemical bond: an interaction that holds 2 atoms together

  4. Combining Atoms • To understand how atoms bond, you need to determine the # of electrons. • Atomic # = # of protons • What else do we know about the atomic #?

  5. Combining Atoms • Electrons are arranged in levels. • Not all electrons in an atom make bonds. • Most atoms form bonds with valence electrons.

  6. Forming a Compound: Example # 1 (K and F)

  7. Combining Atoms • Elements are grouped based on similar properties. • Within a group, atoms have the same number of valence electrons. • Group numbers help you determine the number of valence electrons.

  8. Combining Atoms • Not all atoms bond the same way. • The # of electrons in the outermost shell determines if an atom will bond. • What group of atoms is not likely to form bonds? Why? • What group/groups are more likely to form bonds? Why?

  9. Forming a Compound: Example # 2 (H, He, C, and Ne)

  10. Combining Atoms • Atoms bond by gaining, losing, and sharing electrons. • Their goal is to fill the outermost energy level. • A filled outermost level contains ____ electrons.

  11. Combining Atoms • Not all atoms need 8 electrons to have a full outer level. • The outermost energy level of helium only has 2 electrons and it is full. • How is this true for helium?

  12. Ch. 11 Section 1: Review Questions • 1) What are all substances made up of? • 2) Why is understanding the number of electrons in an element important? • 3) How are elements grouped? • 4)T/F All atoms bond the same way. • 5) How do atoms bond? • 6)How do most atoms form bonds? • 7) T/F All electrons in an atom can make bonds.

  13. Section 2: Objectives • Explain how ionic bonds form. • Describe how positive ions form. • Describe how negative ions form. • Explain why ionic compounds are neutral.

  14. Chemical Bonds • Ionic bond: bond that is formed when electrons are transferred from one atom to another • These form so that the outermost energy level is filled. • What does the name of the bond sound like?

  15. Chemical Bonds • An atom is neutral because the number of electrons equals the number of protons. • The transfer of electrons causes the number of electrons and the charge to change. • Ion: charged particle that forms when an atom or group of atoms gains or loses one or more electrons

  16. Chemical Bonds • Most metals have few valence electrons. • Metal atoms tend to lose their valence electrons and form positive ions.

  17. Chemical Bonds • Energy is needed to pull electrons away from atoms. • Only a small amount of energy is needed to take electrons from metal atoms. • That is why elements in Groups 1 and 2 react easily.

  18. Chemical Bonds • Some atoms gain electrons from other atoms during chemical changes. • These atoms then have more electrons than protons. • What does this mean for their charge?

  19. Chemical Bonds • The outermost energy level of a non-metal is almost full. • They only need a few electrons in order to be full. • Nonmetals tend to gain electrons from other atoms.

  20. Chemical Bonds • Energy is given off when non-metals gain electrons. • Group 17 elements give off the most energy when they gain an electron.

  21. Chemical Bonds • When ionic compounds form, the # of electrons lost by the metal atoms equals the number gained by the non-metal atoms. • The ions that bond are charged, but the compound is neutral. • Crystal lattice: regular pattern in which a crystal is arranged

  22. Chemical Bonds • Most things, such as water and sugar, are held together by covalent bonds. • Low melting and boiling points. • Brittle in solid state.

  23. Chemical Bonds • Covalent bond: formed when atoms share one or more pairs of electrons • In non-metals, atoms don’t donate electrons to form a bond with another non-metal because it requires too much energy. • Non-metals share electrons (covalent bonds).

  24. Chemical Bonds • A molecule consists of 2 or more atoms combined in a definite ratio. • Most atoms are composed of molecules of 2 or more different elements. • A compound can form from a combination of 2 or more atoms of different elements.

  25. Chemical Bonds • An ion is an atom that is no longer neutral because it has gained or lost V.E. • How will changing the V.E. number affect the charge(s) of the atom? • How will changing the V.E. number affect the properties of the atom? (R/U?) • An isotope is a form of an atom that has the same number of protons but a different number of neutrons.

  26. Chemical Bonds • One way to represent atoms is to draw a Lewis-Dot Structure. • Lewis-Dot Structures help you predict how atoms might bond. • To draw: write the element symbol and draw dots for every V.E.

  27. Chapter 11 Sec. 1-2 Recap • 1) What must we determine to understand how atoms bond? • 2) T/F All electrons in an atom form bonds. • 3) How do you determine the # of valence electrons? • 4) How are elements grouped on the periodic table? • 5) What is needed to pull electrons away from atoms?

  28. Chapter 11 Sec. 1-2 Recap • 6) List 2 characteristics of covalent compounds. • 7) An ion will never have a charge of __. • 8) T/F Ionic compounds always have a neutral charge. • 9) Why are Lewis-Dot Structures helpful? • 10) T/F Most metals have few valence electrons.

  29. Section 3: Objectives • Explain how covalent bonds form. • Describe molecules. • Explain how metallic bonds form. • Describe the properties of metals.

  30. Covalent and Metallic Bonds • Most compounds are held together by covalent bonds • Examples: • Water (H2O) • Sugar • Compounds held together by covalent bonds tend to have low melting and boiling points. • This is why oxygen is a gas at room temperature.

  31. Covalent and Metallic Bonds • Substances containing covalent bonds consist of individual particles called molecules. • A molecule usually consists of 2 or more atoms joined in a definite ratio. • However, most molecules are composed of atoms or 2 or more elements.

  32. Covalent and Metallic Bonds • A metallic bond is formed by the attraction between positively charged metal ions and the electrons in the metal. • Positively charged metal ions form when metal atoms lose electrons. • Metallic bonding is what gives metals their properties.

  33. Covalent and Metallic Bonds • Properties of most metals: • Good conductors of heat/electricity • Ductile • Malleable (ability to be reshaped) • Ex 1) Copper is made into wires for electrical cords. • Ex 2) Aluminum can be pounded in sheets.

  34. Covalent and Metallic Bonds • Diatomic molecules are molecules that contain 2 atoms of the same element. • Examples: • O2 (Oxygen) • H2 (Hydrogen) • N2 (Nitrogen) • Cl2 (Chlorine)

  35. Chapter 11 Sec. 3 Recap • 1) What type of bond holds most compounds together? • 2) T/F Most molecules are composed of 2 or more of the same element. • 3) When metals lose electrons, what forms? • 4) What is malleability? • 5) List 1 example of a diatomic molecule.

  36. Chapter 11 Vocabulary Review • 1) _____: an atom that is no longer neutral because it has lost or gained valence electrons • 2) _____: a bond that is formed when many metal atoms share their pooled valence electrons • 3) _____: an outermost electron of an atom that participates in chemical bonding

  37. Chapter 11 Vocabulary Review • 4) ______: a force that holds 2 or more atoms together • 5 _______: a model that represents valence electrons in an atom as dots around the element’s chemical symbol • 6) ______: a group of atoms held together by covelent bonding that acts as an independent unit

  38. Chapter 11 Vocabulary Review • 7) _____: a molecule that has a partial positive end because of unequal sharing of electrons • 8) _____: the attraction between positively and negatively charged ions in an ionic compound • 9) _____: a chemical bond formed when 2 atoms share 1 or more pairs of valence electrons • 10) ____: a group of chemical symbols and numbers that represent the elements and the number of atoms of each element in a compound

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