1 / 28

Covalent Bonds

Covalent Bonds. http://www.ptable.com. Octet Rule must be satisfied-reach noble gas state What of elements that meet and cannot completely transfer e- and satisfy octet rule for each? H and H atom story…one happy if e- tranfer other sad. Both atoms get one e-

orenda
Télécharger la présentation

Covalent Bonds

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Covalent Bonds

  2. http://www.ptable.com • Octet Rule must be satisfied-reach noble gas state • What of elements that meet and cannot completely transfer e- and satisfy octet rule for each? • H and H atom story…one happy if e- tranfer other sad

  3. Both atoms get one e- • Both satisfy octet rule by SHARING • Each atom must have both e- • DIRECTIONAL bond- product of shared e- • Each H atom will have full outer energy level

  4. Hydrogen gas H2 • Two H atoms sharing each other’s e-

  5. Oxygen gas shares 4 valence e- or 2 pairs valence e- • Results in a double bond • Nitrogen gas shares 3 pairs of valence e- • Results in triple bond • Hydrogen, fluorine, nitrogen, chlorine… • BrINClOF (Chlorine is capital C lower case l)

  6. Remember how to do this?1s2… • Each bond represents 2 shared e-

  7. Nature of Covalent Bonds • Strong electrostatic attraction between shared valence e- and + nucleus • One end of molecule has more + than – charge

  8. Draw Lewis dots and show how water molecule shares e- • Covalent bond VERY STRONG • Shared e- confined so bond is DIRECTIONAL

  9. Covalent vs. Ionic Bonds • http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/bom1s2_11.swf

  10. http://www.bing.com/videos/search?q=ionic+vs+covalent+bonding&FORM=VIRE3&adlt=strict#view=detail&mid=D0981F9E5http://www.bing.com/videos/search?q=ionic+vs+covalent+bonding&FORM=VIRE3&adlt=strict#view=detail&mid=D0981F9E5 • video

  11. H tends to share only e- Octet rule not satisfied by giving up e- • H and Cl… HCl • Chlorine tends to grab at e- • Doesn’t want to give it up… • Uneven distribution of e- density • ELECTRONEGATIVITY becomes important ᵟsmall delta indicates charge – or + ᵟ+ H Cl ᵟ-

  12. Result is… • POLARITY • A partial charge separation • Electronegativity increases e- moves towards the area • In covalent bonds, neither atom has energy to remove e- from other atom

  13. Example of a polar covalent molecule • H-O-H Water H2O • Stable octet for oxygen.. Completed with other H atom

  14. Notice how directional the bonds are for water- a covalent molecule • Polarity of water makes it the universal solvent.. Able to dissolve many substances.. • Not all!!

  15. Non Polar Molecules • Even distribution of charge • Examples: oxygen gas O2

  16. Cov vs. Ionic Bonds Electronegativity counts • Hydrogen Gas molecule: H2 No difference of attraction of electrons between 2 atoms so ΔEN=O (Capital Delta Δ means change) Hydrogen gas is a non polar covalent molecule Water is polar covalent

  17. EN and bond types • 0 = non polar cov • < 0.3 no polar cov • 0.3- 0.4 slightly polar cov • 1.0-1.7 polar cov • More and more separation of charges • If difference > 1.7 then generally ionic!

  18. Go to ptable.com • http://www.ptable.com

  19. Your Turn • Use EN # on PT to determine difference in EN between elements of a compound and type of bond formed between them. NaBr Water CS2

  20. Inter and Intra prefixes • Forces may be intra or intermolecular in nature. • H:H molecule of hydrogen gas • Can 3rd H come into the molecule? • No Pauli Exclusion Principle • Molecules formed with hydrogen gas. • Bond very strong .. What’s in between molecules?

  21. BLACK Intra Forces-within molecule-RED Inter Forces- between or among molecules as they exist in natural state Intermolecular forces weaker than intramolecular forces The unit formed is called a molecule

  22. Properties of Covalent (diatomic) Elements and Compounds • Dull no free e- • Soft, brittle- weak intermolecular forces • Low mp and bp- weak intermolecular forces • NO conductivity as solid or molten (no charges) • Some soluble in water Aqueous solutions DO NOT conduct electricity at all- no free moving charged particles

  23. Diamond and graphite examples of Carbon in covalent bonding • Microstructures in diamond very different from graphite • Both covalent, both made of carbon only • Diamond- strong interactions of directionality of carbon atoms- lattice like STRONG BONDS • Graphite- weaker bonds due to direction and spaces between atoms allows for breakage- leaving of powder from pencil

  24. diamond

  25. graphite

  26. Molecular Compounds Nomenclature • State how many of each element in compound • Water H-O-H • FIRST: must know prefixes: • 1. Mono • Di • Tri • Tetra • Penta • Hexa • Hepta • Octa • Nona • Deca

  27. Communicate first element • Assume same name as element’s name • 2nd element “ide” notation • ONE exception: if 1 is coefficient for 1st element then it is dropped • WATER? Dihydrogen monoxide

  28. Your Turn • N2O5 • Carbon dioxide.. To write this formula properly, what is dropped? • Sulfur trioxide • SF6

More Related