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36 terms

Chapter 5 Covalent Bonds and Molecular Structure

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Covalent Bond
A bond that results from the sharing of electrons between atoms (valence electrons)
Molecule
The unit of matter held together by covalent bonds. The electrons from 1 atom are attracted to the protons of another atom.
Structural Formula
Graphic representation of a molecule showing atoms, bonds and their relative arrangement.
Chemical Formula
Written representation of a molecule's atoms.
Bond Dissociation Energy
The energy needed to completely break a covalent bond in a molecule in the gaseou state.
Ionic Compound Properties
High melting point in solids, dissolve in water to form ions, solutions of ions are good conductors of electricity
Covalent Compound Properties
Low melting points, contains solids liquids and gases, strong internal covalent bonds but weak intermolecular bonds.
Electronegativity
How hard an atom "pulls" on the electrons. Has to do with the atoms affinity for electrons.
Periodic Trends of Electronegativity
F pulls hardest (top right), Cs pulls least (bottom left)
Polarity
If the electrons are pulled to one side more than the other, one side of a bond has more negative (d-) while the other has more positive (d+)
Naming Molecular Compounds
1. Cation like comes first, then anion like.
2. Cation like keeps elemental name
3. Anion like gets "ide" ending
4. Prefixes are used to specify number of each atom (anion)
Lewis Dot Structures
Drawing of molecules where electrons are shown as dots around elemental symbols
Non-bonding Pairs
Lone pairs of electrons around their respective atom.
Resonance
When one Lewis structure is not enough. Example O3
Resonance Structure
Square brackets around molecule with double-sided arrow to signify resonance
Formal Charge
A convenient way of assigning charges to individual atoms in a molecule. =column - things
Valence Shell Electron Pair Repultion Theory
VSEPR. All pairs of electrons get the maximum amount of space available.
Linear
Two charge system
Trigonal Planar
Three charge system
Tetrahedral
Four charge system
Trigonal Bipyramidal
Five charge system
Octahedral
Six charge system
Bent
Three charge system with two atoms around central atom and one lone pair of electrons
Trigonal Pyramidal
Four charge system with three atoms around central atom and one lone pair of electrons
Bent
Four charge system with two atoms around center atom and two lone pairs of electrons
See Saw
Five charge system with four atoms around central atom and one lone pair of electrons
T shaped
Five charge system with three atoms around central atom and two lone pairs of electrons
Bent
Five charge system with two atoms around central atom and three lone pairs of electrons
Square Pyramidal
Six charge system with five atoms around central atom and one lone pair of electrons
Square Planar
Six charge system with four atoms around central atom and two lone pairs of electrons
T shaped
Six charge system with three atoms around central atom and three lone pairs of electrons
Linear
Six charge system with two aroms around central atom and foour lone pairs of electrons
Valence Bond Theory
Used to describe the way electrons are shared in covalent bonds
Sigma Orbitals
Result from head-on overlap of atomic orbital between 2 nuclei
Pi Orbitals
Result from edge on (sideways) overlap of atomic orbitals (d or p orbitals)
Molecular Orbital Theory
Atomic orbitals combine to form these orbitals. Has two types: bonding and anti bonding