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Objectives

Objectives. Introduction to Chemical Bonding. Chapter 6. Define chemical bond. Explain why most atoms form chemical bonds. Describe ionic and covalent bonding. Explain why most chemical bonding is neither purely ionic nor purely covalent.

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Objectives

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  1. Objectives Introduction to Chemical Bonding Chapter 6 Define chemical bond. Explain why most atoms form chemical bonds. Describe ionic and covalent bonding. Explain why most chemical bonding is neither purely ionic nor purely covalent. Classify bonding type according to electronegativity differences.

  2. What is bonding? • Bonding is the “glue” that hold two or more elements together • This “glue” is most likely formed as a result of a chemical reaction • Bonding and molecular structure play a central role in determining the course of chemical reactions

  3. What is a bond? • A bond can be thought of as a force that holds groups of two or more atoms together and makes them function as a unit • Example : water O Bonds require energy to break and release energy when made H H

  4. Why do atoms bond?

  5. Atoms bond because bonding lowers the atom’s potential energy.

  6. Bond Energy is the energy required to break chemical bonds -is an endothermic process -requires energy -endothermic process -bond energy values are postive

  7. Bond Formation -is a energy releasing process -exothermic process -the values for bond formation are negative

  8. Bond Length Is the distance between bonded atoms Bond length and bond energy are indirectly related.

  9. IONIC BONDING Chemical bonding resulting from the electrical attraction between cations and anions.

  10. Three Types of Bonds • Ionic • Covalent • Metallic

  11. Visual Concepts Chapter 6 Ionic Bonding

  12. Ionic Bonds • Na and Cl • Na is a metal and likes to lose one electron • Cl is a nonmetal and likes to gain one electron • the final ionic compounds is NaCl Na+ Cl- NaCl + The electrostatic interaction keeps them together!

  13. Ionic Bonds • Na looses an electron and chlorine gains it! • They do this to achieve an octet! Na Cl

  14. Covalent Bonds • Covalent Bonds • exist between nonmetals bonded together • form when atoms of nonmetals share electrons • electrons can be shared equally or unequally

  15. Types of Covalent • Polar • Nonpolar • Network Covalent

  16. Visual Concepts Chapter 6 Covalent Bonding

  17. Metallic Bonds • Metallic bonds exist between metals • Occur when two metals, usually the same metal, are bonded together

  18. IONIC OR COVALENT? How can you tell?

  19. The type of bond can usually be calculated by finding the difference in electronegativity of the two atoms that are going together.

  20. Visual Concepts Chapter 6 Using Electronegativity Difference to Classify Bonding

  21. Electronegativity Difference • If the difference in electronegativities is between: • 1.7 to 4.0: Ionic • 0.3 to 1.7: Polar Covalent • 0.0 to 0.3: Non-Polar Covalent • Example: NaCl • Na = 0.8, Cl = 3.0 • Difference is 2.2, so • this is an ionic bond!

  22. Visual Concepts Chapter 6 Comparing Polar and Nonpolar Covalent Bonds

  23. Bonding and Ionic Compounds Chapter 6 Ionic Vs. Covalent Bonding

  24. Bonds Between Atoms Polyatomic Ions Ionic Covalent Metallic Molecular Substance Network Solids Polar Nonpolar What are we going to learn about???

  25. Marriage Forming of a bond is like marriage The breaking of a bond relates to a divorce. • More stable • exothermic Divorce • Less stable • Endothermic

  26. Compare and Contrast • Ionic and Covalent Compounds

  27. PROPERTIES OF IONIC COMPOUNDS Ionic compound – is composed of positive and negative ions that are equal in charge. Formula Unit – is the simplest collection of atoms from which an ionic compound’s formula can be established.

  28. Properties of Ionic Bonds • What is an Ionic Bond? • - An Ionic Bond is a chemical bond resulting from the TRANSFER of electrons from one bonding atom to another • When is an ionic bond formed? - An ionic bond is formed when a cation (positive ion) transfers electrons to an anion (negative ion).

  29. What are some characteristics of an ionic bond? • Exist as crystalline units at room temperatures • Brittle • Have higher melting points and boiling points compared to covalent compounds . Melting points are 1000 ˚C • Conduct electrical current in molten or solution state but not in the solid state • The smallest piece of an ionic compound is a formula unit.

  30. What are some characteristics of an ionic bond? 6. A formula unit is the smallest collection of atoms from which a formula can be established. 7. Usually dissolves in polar solvents such as water. This is called dissociation. 8. The best way to test for an ionic compound is electrical conductivity in solution. Formula Units of salt

  31. Dissolving of salt in water - Dissociation

  32. Properties of Ionic Compounds Lattice energy- is the energy released when one mole of an ionic crystalline compound is formed from gaseous ions.

  33. Properties of Ionic Compounds Lattice energy values are negative. The more negative the value the stronger the ionic bond.

  34. Covalent Bonds • What is an Covalent Bond? • - A covalent bond is a chemical bond resulting from SHARING of electrons between 2 bonding atoms. • What forms a covalent bond? - A covalent bond is formed between two nonmetals.

  35. There are five different categories associated with covalent bonds. What are the 5 different categories? Covalent Network Solids Molecular Substance Polar Coordinate Covalent Nonpolar

  36. What are some characteristics of a covalent bond? • Very strong • Low melting and boiling points • Below 500 ˚C • Exist as solids, liquids, or gases at room temperature • Do not conduct electricity unless it is a molecular electrolyte (acid or base) • Molecular electrolytes undergo ionization in polar solvents acids and bases.

  37. Ionization of Molecular Acids in Water.

  38. Section3 Ionic Bonding and Ionic Compounds Chapter 6 Melting and Boiling Points of Compounds

  39. Covalent Bonds can have multiple bonds, so you should be familiar with the following… Single Covalent Bond- chemical bond resulting from sharing of an electron pair between two atoms. Double Covalent Bond- chemical bond resulting from sharing of two electron pairs between two atoms. Triple Covalent Bond-chemical bond resulting from sharing of three electron pairs between two atoms. Triple bonds are the strongest and shortest

  40. First, we are going to look at Polar Covalent… c What is polar covalent? -Polar covalent is a description of a bond that has an uneven distribution of charge due to an unequal sharing of bonding electrons. The boy is not equally sharing with anyone else but rather taking all the food for himself.

  41. Next, we are going to look at Non-Polar Covalent… What is non-polar covalent? -Non polar covalent is a covalent bond that has an even distribution of charge due to an equal sharing of bonding electrons. This couple is non- polar because they are sharing the drink equally between them.

  42. Now, we are going to look at Network Solids… Diamond and graphite are examples of network covalent compounds. What is a Network Solid? -A network solid is a solid that has covalently bonded atoms linked in one big network or one big macromolecule. Name 3 Characteristics of a Network Solid. • Poor conductors of heat and electricity • Hard / Strong • High melting and boiling points

  43. Just as a summary to what each bond looks like…

  44. Properties of Metallic Bond The Metallic-Bond Model The chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons is called metallic bonding.

  45. Metallic Bonding Name 4 Characteristics of a Metallic Bond. What is a Metallic Bond? - A metallic bond occurs in metals. A metal consists of positive ions surrounded by a “sea” of mobile electrons. • Good conductors of heat and electricity • Great strength • Malleable and Ductile • Luster This shows what a metallic bond might look like.

  46. Properties of Metals: Malleability and Ductility

  47. Metallic Bonding Malleability is the ability of a substance to be hammered or beaten into thin sheets. Ductility is the ability of a substance to be drawn, pulled, or extruded through a small opening to produce a wire.

  48. Metallic Bonding • Chemical bonding is different in metals than it is in ionic, molecular, or covalent-network compounds. • The unique characteristics of metallic bonding gives metals their characteristic properties, listed below. • electrical conductivity • thermal conductivity • malleability • ductility • shiny appearance

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