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Covalent Bonding Skeleton Diagrams

Covalent Bonding Skeleton Diagrams. Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology. Only the noble gases have exactly the correct number of electrons to fill their outermost s and p orbitals. All other atoms have to lose, gain or share

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Covalent Bonding Skeleton Diagrams

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  1. Covalent BondingSkeleton Diagrams Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology

  2. Only the noble gases have exactly the correct number of electrons to fill their outermost s and p orbitals. All other atoms have to lose, gain or share electrons to attain the stability associated with the noble gases.

  3. Atoms which gain or lose electrons are called ions. An ionic bond is the electrostatic attraction that holds ions together. A covalent bond is the sharing of electrons between two atoms. Atoms share electrons to attain the electronic configuration and stability of a noble gas. Each atom has a tendency to form a certain number of bonds in stable, neutral compounds.

  4. Kernal Skeleton Bonds diagram diagram H H - • Li 1 Li Li - • Be 2 Be - Be - • • • B 3 B - B - • • Bonding Tendencies H 1

  5. Kernal Skeleton Bonds diagram diagram • C 4 C • • - C - • • • - N - N N 3 • • • • • O • • O 2 - O - • • • • • F F 1 F - • • • • Bonding Tendencies

  6. Skeleton Diagrams • These atoms are neutral in charge. • Only outer shell (valence) electrons are included. • Each atom tends to form a specific number of bonds when it forms a molecule. • Often, an unique atom is at the center of the structure.

  7. hydrogen – represents a single bond H – F fluoride between two atoms represents a double bond = carbon O=C=O (i.e., two bonds) between the dioxide same two atoms º represents a triple bond boron B º N (i.e., three bonds) between nitride the same two atoms beryllium Be=O Skeleton diagrams provide some information about the strength of the bond. oxide Skeleton Diagrams of Molecules Skeleton diagrams indicate which atoms are bound together.

  8. H methane H H H N ammonia H H C H H H C H H O O formaldehyde water Skeleton Diagrams of Molecules H-C-H bond angle 109.5° H-N-H bond angle 107° H-O-H bond angle 104.5° H-C-H bond angle ~120° Skeleton diagrams do not indicate bond angles!

  9. fluorine 1 155 kJ·mol–1 F – F gas (difluorine) oxygen gas O = O 2 495 kJ·mol–1 dioxygen) ( nitrogen N ºN gas 3 941 kJ·mol–1 (dinitrogen) Skeleton Diagrams of Molecules Bond Order Bond Energy Which gas is the most reactive?

  10. Pairs Activity • A pair of people will work on one problem: • One person is responsible for writing all the information. • The other person is responsible for saying what should be written.

  11. On a card or a piece of paper • Write each sequential step necessary to draw a skeleton diagram. • Number each step. • Amend and update the list. • Either person may do this. Draw the skeleton diagram of acetic acid, CH3COOH

  12. Isomers • An isomer is a compound with the same molecular formula, but different structure. • The atoms are linked differently together. Draw the skeleton diagram of an isomer of acetic acid, CH3COOH

  13. H H H H C C O H H C C O H O O H H H H C O C H O Isomers of C2H4O2 glycolaldehyde acetic acid methyl formate

  14. H H H O C C C H O C C C H H C C O C O O O O H C O O H H H H C C H O O Unstable Isomers of C2H4O2 Small ring structures (containing 3 or 4 atoms in the ring) are either unstable or very reactive

  15. Sodium Acetate • Acetic acid reacts with sodium hydroxide to form sodium acetate and water. Draw the skeleton diagram of sodium acetate.

  16. Draw the skeleton diagrams for • boric acid, H3BO3 • aluminum hydroxide

  17. H O H H O B O H O H H O Al O H3BO3 and Al(OH)3 Compare the Structures of Boric Acid and Aluminum Hydroxide aluminum hydroxide boric acid Both have similar skeleton diagrams, but different chemical properties.

  18. The Periodic StaircaseSeparates Metals and Nonmetals Compare their position on the periodic table. nonmetals metals Boron is a metalloid or semi-metal, whereas aluminum is metallic.

  19. Which bond might break to show each chemical character? H Metal oxides are basic O H H O B O H H O Nonmetal oxides are acidic H H O Al O H O Compare the Structures of Boric Acid and Aluminum Hydroxide Both have amphoteric character.

  20. Skeleton Diagrams • The skeleton bonding approach works for many molecules; • however, it fails to explain the bonding in some simple molecules and ions.

  21. Skeleton Diagrams • What is the skeleton diagram for • carbon monoxide • ammonium ion • cyanide ion • Which atom(s) in each structure breaks the skeleton bonding rules?

  22. or O O C C + + H H or H H H H N N H H or N C N C Skeleton Diagram Failures

  23. N N O O P P S S S S S P S S S P Types of Bonds Formed Lighter members of a family often form multiple bonds Heavier members favor additional single bonds.

  24. O O Si Si O O C O O carbon dioxide Si O O O O Si Si silicon dioxide quartz, glass, sand O Heavier Members of a Familytend to form single bonds

  25. Bonding Theories • Ionic Model • Skeleton Diagrams • Identifies how atoms are linked together • Fails to describe the bonding in ions and certain molecules (e.g., CO, NH4+, CN–) • Fails to explain the geometry of molecules

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