Structure and Properties of Matter Pt2 Flashcards
Coordinate Covalent Bonds
- a covalent bond where both e- are from one atom
Expanded Octet
- atoms period 3 or higher have vacant d orbitals to overfill the octet
Resonance Structures
- Lewis structures that show the same relative position of atoms but different pairs of e- pairs
- blend between structures, not switching between
Two Theories of Covalent Bonding
- Valence bond theory
- Hybridization
Valence Bond Theory
- covalent bonds form when half-filled orbitals overlap
- must have opposite spin
Hybridization
- methane has 4 identical bonds but no e- configuration makes 4 identical bonds
- 1 s orbital and 3 p orbitals hybridize to form 4 sp3 orbitals (takes on tetrahedral shape to minimize e-/e- repulsion
- hybrid orbitals all have the same amount of eng
How to predict
Type of hybridization
- an e- group is any single/double/triple bond or lone pair
- # of e- groups tell you hybridization
Sigma Bond
- formed by the end-to-end overlap of hybridized orbitals
Pi Bond
- overlap of unhybridized p orbitals side-by-side above and below the nuclei
VSEPR Theory
- e- groups around atoms are positioned as far from e/o as possible to minimize e- repulsion
5 main VSEPR shapes w/o lone pairs
- AX2: linear (180)
- AX3: trigonal planar (120)
- AX4: tetrahedral (109.5)
- AX5: trigonal bipyramidal (120 + 90)
- AX6: octahedral (90)
Repulsive forces that affect VSPER theory
LP-LP > LP-BP > BP-BP
lone pairs spread out more and take up more space due to e- repulsion
VSEPR Notation
A = central atom
B/X = surrounding atoms
E = lone pairs
VSEPR shapes with lone pairs
- AX2E: bent (<120)
- AX2E2: bent (<109.5)
- AX2E3: linear (180)
- AX3E: trigonal pyramidal (<109.5)
Ionic Bond
- electrostatic attraction between ions
- ^EN > 1.7
Lattic Energy
- eng released in the formation of ionic bonds
- indicates bond strength (must add a greater amt of eng to break the bond)
- ionic radius: smaller ion = stronger bond
- ionic charge: larger ionic charge = stronger bond
Solubility of ionic compounds
- to be soluble: attractive forces between ions and water must be stronger than the attractive forces between the ions themselves
- larger ionic radius and smaller ionic charge
Mechanical properties of ionic compounds
- hard and brittle (when stressed, charges align and repel)
- conductive when aq, free-flowing ions can carry a charge
Molecular Solids and Allotropes
- similar structure to ionic compounds but are held together by IMF’s
- different form of an element that has different properties
Diamond vs Graphite
Diamond (sp3):
- tetrahedral
- all covalent bonded
- very hard and brittle, high MP/BP
Graphite (sp2):
- unhybridized orbitals overlap to form planes
- delocalized pi electrons
Network Covalent Solids
- continuous array with no natural beginning or end
- hard + brittle
- extremely high MP/BP
- insoluble
- poor conductors
Electron-sea Model
- lattice structure of positive ions and delocalized e- sea
- metallic bond is electrostatic attraction between cation and delocalized e-
Strength of Metallic Bonds
Stronger bonds means:
- more delocalized e-
- larger charge of cation
- smaller cation
Properties of Metallic Compounds
- electrical and thermal conductivity due to e- sea
- malleability and ductility since cations can slide past e/o due to e- sea
