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♪ Ionic – metal + nonmetal♪ Transfer electrons from metal to nonmetal
♪ Metallic – metal + metal♪ Surrounded by sea of electrons
♪ Covalent – nonmetal + nonmetal♪ Share electrons♪ Nonpolar – equally share electrons♪ Polar – unequally share electrons
▲The greater the difference in electronegativity, the greater the ionic character of the bond. (see pg. 151 for table of electronegativities)
▲0 - 0.3 = nonpolar covalent
▲0.31-1.7 = polar covalent
▲1.71 – 3.3 = ionic
Electronegativity Table
♥ NaCl
♥ CO2
♥ CH4
♥ Na = 0.9 Cl = 3.0 ♥ 3.0-0.9 = 2.1 IONIC♥ C = 2.5 O = 3.5 ♥ 3.5-2.5 = 1.0 POLAR
COVALENT♥ C = 2.5 H = 2.1 ♥ 2.5-2.1 = 0.4 POLAR
COVALENT
◘ CaBr2
◘ SeI2
◘ PCl5
◘ LiF
◘ SF6
◘ Ionic◘ Nonpolar Covalent◘ Polar Covalent◘ Ionic◘ Polar Covalent
Bonding – atoms use valence electrons from other atoms to fill their outside orbitals.
Bonding produces lower energy atoms.
Covalent bond – a bond in which two atoms share a pair of electrons.
Characteristics:Occurs mainly between two or more non-metals.
Electrons are shared fairly equally between atoms.
Molecule – neutral group of atoms held together by covalent bondsdiatomic molecule – molecule with 22 atomsmolecular formula –the types of atoms and #s of atoms in a moleculemoleculepotential energy – stored energy bond length – distancedistance between two atoms in a molecule (at minimum potential energy)bond energy – energy used to breakbreak bonds & make neutral atoms (kJ/mol)
Valence electrons are usually the only electrons used in chemical bonds.Only the valence electrons are shown in electron dot structures.Octet Rule – when forming compounds, atoms tend to achieve the electron configuration of a noble gas (eight e-’s in the outer orbital).Exceptions to the Octet Rule: Hydrogen (wants 2 electrons), Boron (usually wants 6), & some atoms that use d orbitals as well as Sulfur and Phosphorous
Gilbert Lewis devised the octet rule to create drawings of atoms and ions.
The Lewis Dot structure of an atom is simply the atom symbol with its valence electrons around it.
Rule – Don’t pair until you have to!!!!!
Unshared/Lone Pair Electrons – valence electrons not used in bonding (belong to one atom only)
Li
B
Si
N
Sodium
Fluorine
Aluminum
Carbon
Phosphorus
Li+1
B +3
O -2
N -3
Loses one electron
Loses three electrons
Gains two electrons
Gains three electrons
Chloride Ion
Aluminum Ion
Cl -1
Al +3
Structural formulas – use a dash to represent 2 electrons and show how atoms are connected.
Double covalent bonds are bonds that involve two shared pairs of electrons.
Example - SiO2
Triple covalent bonds are bonds that involve three shared pairs of electrons.
Example N2
Br2
HF
NH3
CH4
CO2
Draw the electron dot diagram for these molecules.
TV Guide!
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