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Properties low vapor pressures –do not easily evaporate
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Properties of Ionic Compounds
Properties
• high melting points– strong electrostatic interactions between
oppositely charged ions
Properties
• low vapor pressures– do not easily evaporate
Properties• tend to be hard and brittle
– break easily
Properties
• some forms conduct electricity
ionic compound form conducts electricitysolid NO
molten (liquid) YES
aqueous solution YES
Structure of Ionic Compounds• (+/-) ions form crystal lattice
– regular 3-D pattern or array – ions held in fixed positions
(solid state)
• Unit Cell = smallest repetitive unit in lattice
Properties of Metallic Bonding
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…
Na 3s1 Na 3s1
overlapping valence electron orbitals
electrons in outer valence shell electrons in outer valence shell move freely through overlapping move freely through overlapping shells shells
• rresults: esults: • ““sea of mobile electronssea of mobile electrons””• (+) metal cations form
sea of electrons:creates the metallic bond:
•electrostatic attraction between (+) metal cations & sea (-) electrons
Metal Propertiesval e- moving freely from place to place in
sea of mobile electrons allows metals to:● conduct electricity (flow of electrons)● conduct heatalso accounts for metals being:
● malleable ● ductile ● shiney (luster)
apply force to metal structure: • metal atoms shift away from force & free e- keep metal cations from separating and breaking• shape becomes deformed
Metal
apply force to ionic compound structure: • forces like charges to align (+) to (+) & (-) to (-) resulting in shattering due to repulsion forces
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
AlloysAlloys
mixturemixture of elements with metallic properties of elements with metallic propertiesmixture can be adjusted to get desired mixture can be adjusted to get desired
propertiespropertiestwo types:two types:
substitutional and interstitial alloy substitutional and interstitial alloy (depends on size of elements – same or different size)(depends on size of elements – same or different size)
Common alloysbrass: Cu & Znbronze: Cu, Sn & Alpewter: Sn, Pb & Cusolder: Pb & Snrose gold: Cu & Alwhite gold: Au & Ni, Pd or Ptsterling silver: Ag & Custeel: C & Fe
stainless steel: Cr & Ni
Properties of Covalent (Molecular) Substances
Properties
• depend on strength of IMF between “particles” or separate units
• covalent substances:– units are molecules
Intermolecular ForcesIntermolecular Forces• dispersion forcesdispersion forces occur between non-
polar molecules (Van der Waals)
• dipole-dipole forcesdipole-dipole forces occur between polar molecules
• hydrogen bonding forceshydrogen bonding forces occur between molecules with H-F, H-O, or H-N
Remember: IMF determine phase!Remember: IMF determine phase!
weakest IMF = dispersion forces weakest IMF = dispersion forces - occur between - occur between non-polarnon-polar atoms/molecules atoms/molecules
● monatomic atoms:monatomic atoms:● diatomic elements:diatomic elements:● small symmetric molecules:small symmetric molecules:
● hydrocarbon molecules:hydrocarbon molecules:
Reminder:Reminder:dispersion forces dispersion forces ↑↑ as size molecule ↑ as size molecule ↑
He, Ne, Ar, Kr He, Ne, Ar, Kr OO22, H, H22, N, N22
COCO22, CCl, CCl44, , CFCF44
CHCH44, C, C44 H H1010
If a covalent molecule doesnIf a covalent molecule doesn’’t meet the t meet the requirements for a non-polar substance requirements for a non-polar substance
than it is polar than it is polar
and and
will have dipole-dipole IMF or H-bonding forces will have dipole-dipole IMF or H-bonding forces
Properties: Covalent (Molecular) SubstancesProperties: 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
mp, bp, Hmp, bp, Hff and H and Hvv & VP & VP depend on how difficult depend on how difficult it is to separate particles it is to separate particles from each other from each other
weak IMF – easy to separate particles (need less energy) weak IMF – easy to separate particles (need less energy)
strong IMF – difficult to separate particles (need more energy) strong IMF – difficult to separate particles (need more energy)
Which substance has the strongest IMF?Which substance has the strongest IMF?
The weakest?The weakest?How know which is weakest/strongest?How know which is weakest/strongest?
waterwater
etherether
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
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
Diamond Structure
Network Solids: Silicon• silicon can also form network solids
– ex: quartz (SiO2 – AKA sand)
• quartz has very complicated crystal structure