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Chemical Bonding: What and Why

Chemical Bonding: What and Why. F. Schifano , Department of Science Bayonne High School Bayonne, NJ 07002. This Unit Will Be Nine Days Long. This Unit Addresses Key Standards.

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Chemical Bonding: What and Why

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  1. Chemical Bonding: What and Why F. Schifano, Department of Science Bayonne High School Bayonne, NJ 07002

  2. This Unit Will Be Nine Days Long

  3. This Unit Addresses Key Standards • NJCCCS 5.2.12.B.1.(...chemical bonds are the interactions between atoms that hold them together in molecules or between oppositely charged ions.)

  4. Key Skills

  5. What is a chemical bond? • A chemical bond is a relationship between two or more atoms that involves the transfer or sharing of electrons.

  6. How are bonds related to chemical reactions? • Chemical reactions are the observable consequences of making and breaking bonds. • The formation or breaking of a bond results in a chemical change– an energy change and the production of a new product substance.

  7. Enthalpy (H) • Enthalpy is the potential energy stored in chemical bonds. • Chemical reactions release or absorb heat because the total enthalpy in the reactants is different than the total enthalpy of the products.

  8. What isn’t a chemical bond? • Mixtures are combinations of atoms that involve only physical jumbling rather than chemical bonding. • Formed and separated by physical changes

  9. What isn’t a chemical bond? • Intermolecular forces– weak, transient interactions between molecules control some physical, but not chemical properties. • Next unit we will focus on these.

  10. Why do atoms form bonds? • Atoms form bonds because in doing so they can rearrange their electrons in a way that makes them more stable. • Bonds are a way for atoms to achieve valence = 8. • Hydrogen is stable at VAL=0 or VAL =2 • Boron is stable at VAL = 6

  11. Showing Bonds: 3D Models

  12. Lewis Structures • Gilbert Lewis (ENG-1916) invented the structures to show on paper how molecules were bonded.

  13. Reading Lewis Structures • Lines represent covalent bonds. Each line counts as two electrons. • Dots represent unshared electrons. • Unshared pairs are called lone pairs.

  14. Writing Lewis Structures • Atoms have different needs to achieve stability so they will form different numbers and kinds of bonds.

  15. Covalent Bond Behaviors You should copy this slide to your formula sheet.

  16. Writing Lewis Structures

  17. Step-By-Step Lewis Structures • Write the highest bond order element in the center. • Attach all other high-bond order elements to this central atom by single bonds. • Show all missing bonds as empty lines. • Use any available 1-bond order elements to fill up empty bonds. • If there are any empty bonds on adjacent molecules, use multiple bonds to fill them.

  18. Practice • Write the Lewis structures of each of the following substances.

  19. Practice

  20. Practice

  21. Practice

  22. Practice

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