Properties of Ionic Compounds Properties high melting points
- Slides: 30
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 electricity solid 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 3 s 1 overlapping valence electron orbitals
electrons in outer valence shell move freely through overlapping shells • results: • “sea of mobile electrons” • (+) metal cations form
sea of electrons: creates the metallic bond: • electrostatic attraction between (+) metal cations & sea (-) electrons
Metal Properties val e- moving freely from place to place in sea of mobile electrons allows metals to: ● conduct electricity (flow of electrons) ● conduct heat also accounts for metals being: ● malleable ● ductile ● shiney (luster)
apply force to Metal 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
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
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)
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
Properties of Covalent (Molecular) Substances
Properties • depend on strength of IMF between “particles” or separate units • covalent substances: – units are molecules
Intermolecular Forces • dispersion forces occur between polar molecules (Van der Waals) non- • dipole-dipole forces occur between polar molecules • hydrogen bonding forces occur between molecules with H-F, H-O, or H-N Remember: IMF determine phase!
weakest IMF = dispersion forces - occur between non-polar atoms/molecules He, Ne, Ar, Kr O 2, H 2, N 2 ● diatomic elements: CO 2, CCl 4, CF 4 ● small symmetric molecules: ● ● monatomic atoms: hydrocarbon molecules: CH 4, C 4 H 10 Reminder: dispersion forces ↑ as size molecule ↑
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
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
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)
Which substance has the strongest IMF? water The weakest? ether How know which is weakest/strongest?
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 (Si. O 2 – AKA sand) • quartz has very complicated crystal structure
- Why do ionic compounds have high melting and boiling points
- Brittleness of ionic solids
- Ionic compound
- Venn diagram of ionic and covalent bonds
- Ionic compounds
- Properties of ionic compounds
- Ionic bonds hardness
- Incongruent melting example
- Difference between metal oxides and non metal oxides
- Reactivity of group 1
- The melting point of ice
- Mixed melting point
- Criss cross method steps
- Ternary ionic compounds
- What is a monatomic ion
- Solubility vs solubility product
- Ionic compounds
- Steps to naming ionic compounds
- How do you name an ionic compound
- Naming chemical compounds
- Ternary ionic compounds
- Review- naming chemical compounds
- Binary ionic compounds
- Getting connected ionic compounds
- Name it
- Why do ionic compounds form crystals
- Examples ionic compounds
- Unit chemical bonding forming ionic compounds ws 2
- Rules for naming ionic compounds
- Why can molten ionic compounds be electrolysed
- Ionic vs covalent compounds