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Properties of Ionic Compounds

Properties of Ionic Compounds. Properties. high melting points strong electrostatic interactions between oppositely charged ions. Properties. low vapor pressures d o not easily evaporate. Properties. tend to be hard and brittle b reak easily. Properties.

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Properties of Ionic Compounds

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  1. Properties of Ionic Compounds

  2. Properties • high melting points • strong electrostatic interactions between oppositely charged ions

  3. Properties • low vapor pressures • do not easily evaporate

  4. Properties • tend to be hard and brittle • break easily

  5. Properties • some forms conductelectricity

  6. Structure of Ionic Compounds • (+/-) ionsform crystal lattice • regular 3-D pattern or array • ions held in fixed positions (solid state) • Unit Cell = smallest repetitive unit in lattice

  7. Properties of Metallic Bonding

  8. Metal bonding • Metals: form organized lattice structures similar to ionic cmpds • adjacent atoms in metal lattice are all same • close proximity of atoms allows outer electron energy levels to overlap So…

  9. Na 3s1 Na 3s1 overlapping valence electron orbitals

  10. electrons in outer valence shell move freely through overlapping shells • results: • “sea of mobile electrons” • (+) metal cations form

  11. creates the metallic bond: • electrostatic attraction between (+) metal cations & sea (-) electrons sea of electrons:

  12. Metal Properties val e- moving freely from place to place in sea of mobile electrons allowsmetals to: • conduct electricity (flow of electrons) • conduct heat • also accounts for metals being: • malleable • ductile • shiney (luster)

  13. Metal apply force to metal structure: • metal atoms shift away from force & free e- keep metal cations from separating and breaking • shape becomes deformed apply force to ionic compound structure: • forces like charges to align (+) to (+) & (-) to (-) resulting in shattering due to repulsion forces

  14. as # of electrons that can be delocalized ↑ so does: Hardness and Strength Na has one valence electron that can be delocalized so: - is relatively soft ( can be cut with a butter knife) Mg has two valence electrons that can be delocalized so: - still can be cut but is much harder than Na transition metals have varied # of e-'s that can be delocalized - chromium (Cr+6) is very hard and has high strength

  15. Alloys • mixture of elements with metallic properties • mixture can be adjusted to get desired properties • two types: • substitutional and interstitial alloy • (depends on size of elements – same or different size)

  16. Common alloys brass: Cu & Zn bronze: Cu, Sn & Al pewter: Sn, Pb & Cu solder: Pb & Sn rose gold: Cu & Al white gold: Au & Ni, Pd or Pt sterling silver: Ag & Cu steel: C & Fe stainless steel: Cr & Ni

  17. Properties of Covalent (Molecular) Substances

  18. Properties • depend on strength of IMF between “particles” or separate units • covalent substances: • units are molecules

  19. Remember: IMF determine phase! Intermolecular Forces • dispersion forces occur between non-polar molecules (Van der Waals) • dipole-dipole forces occur between polar molecules • hydrogen bonding forces occur between molecules with H-F, H-O, or H-N

  20. weakest IMF = dispersion forces - occur between non-polar atoms/molecules • monatomic atoms: • diatomic elements: • small symmetric molecules: • hydrocarbon molecules: He, Ne, Ar, Kr O2, H2, N2 CO2, CCl4, CF4 CH4, C4 H10 Reminder: dispersion forces ↑ as size molecule ↑

  21. If a covalent molecule doesn’t meet the requirements for a non-polar substance than it is polar and will have dipole-dipole IMF or H-bonding forces

  22. Properties: Covalent (Molecular) Substances • poor conductors: heat & electricity • no charged particles! • low mp & low bp: • easy to pull molecules apart from each other • low Hf and Hv: • not much energy needed to change phase • high VP: • evaporate easily • majority of solids are soft

  23. mp, bp, Hf and Hv & VP depend on how difficult it is to separate particles from each other strong IMF – difficult to separate particles (need more energy) weak IMF – easy to separate particles (need less energy)

  24. water ether Which substance has the strongest IMF? The weakest? How know which is weakest/strongest?

  25. NETWORK SOLIDS • carbon and silicon form extensive networks, similar to a crystal lattice • different physical properties than molecular compounds: • hard rather than soft (except graphite) • high mp & bp, high Hf & Hv • similar physical properties than molecular cmpds: • non-conductors

  26. NETWORK SOLIDS: Carbon • most covalent substances are molecular • carbon forms 4 bonds with 4 other C atoms • allows C to build up extensive network • ex: diamond, graphite • super strong covalent bonds hold atoms together

  27. Diamond Structure

  28. Network Solids: Silicon • silicon can also form network solids • ex: quartz (SiO2– AKA sand) • quartz has very complicated crystal structure

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