Covalent Bonding Flashcards

Terms Definitions
sulfur trioxide
hydrogen peroxide
hydrogen chloride
carbon monoxide
VSEPR theory
valence-shell electron-pair repulsion theory; because electron pairs repel, molecules adjust their shapes so that valence-electron pairs are as far apart as possible
hydrogen bond
a relatively strong intermolecular force in which a hydrogen atom that is covalently bonded to a very electronegative atom is also weakly bonded to an unshared electron pair of another electronegative atom in the same molecule or one nearby
molecular orbitals
an orbital resulting from the overlapping of atomic orbitals when two atoms combine
dispersion force
the weakest find of intermolecular attraction; this attraction is thought to be caused by the motion of elections
3 0 3
Trigonal Planar/ Trigonal Planar/ 120/ sp2/ Ex: AlCl3, SO3
4 0 4
Tetrahedral/ Tetrahedral/ 109.5/ sp3/ Ex: CH4
bonding orbital
a molecular orbital whose energy is lower than that of the atomic orbitals from which it is formed
unshared pairs
pairs of valence electrons that are not shared between atoms; aka lone pairs or nonbonding pairs
sp2-hybridized orbital
Central atom singly or doubly bonded to three other atoms is sp2-hybridized. Trigonal planar.
2 0 2
Linear/ Linear/ 180/ sp/ Ex: BeCl2
Step 1 to VSEPR Theory
1. Draw Lewis Structure
polar bond
a bond formed when two different atoms are joined by a covalent bond and the bonding electrons are shared unequally
polar molecule
a molecule, like water, in which one or more atoms is slightly negative and one or more is slightly positive, unless molecular geometry causes the polarities to cancel each other out
tetrahedral angle
a bond angle of 109.5 degrees created when a central atom forms four bonds directed toward the corners of a regular tetrahedron
Sigma orbitals and bonds
Are cylyndrical around the axis joining the two nuclei and result from the overlap of two s-orbitals, two p-orbitals, or an s and a p-orbital, or the overlap of other hybrid orbitals.
Bond length comparison
propane, C-H 110 pm, C-C 153 pm
propene, C-H 108 pm, C=C 134 pm
propyne, C-H 106 pm, carbon-carbon triple bond 121 pm
Average bond energy and ΔrH
Determined experimentally by measuring the average covalent bond energies for a variety of typical molecules. Useful for estimating enthalpy changes in reactions.
CH2=CH2 + H-H ==> CH3-CH3, ΔrH = -31
Bonds broken:
C=C, +146kcal/mol
H-H, +104kcal/mol
Bonds formed:
C-C, -83 kcal/mol
2 x C-H, -99 kcal/mol
Total enthalpy of reaction, ΔrHo = -31, which means it's exothermic because it gives off more energy than it consumes.
1 2 3
Trigonal Planar/ Paired/ N/A / sp2/ Ex: O2
double covalent bonds
bonds that involve two shared pairs of electrons
1 1 2
Linear/ Paired/ N/A / sp/ Ex: CO, N2
nonpolar covalent bond
a bond formed when the atoms in a molecule are alike and the bonding electrons are shared equally
Step 2 to VSEPR Theory
2. Count Electron pairs and arrange them to minimalize repulsion
Step 4 to VSEPR Theory
4. Determine the name of the molecular structure from how the atoms are arranged
single covalent bond
a bond in which two atoms share a pair of electrons
Pi orbitals and bonds
Have a nodal plane and result from the sideways overlap of two p-orbitals. sp2-hybridized carbon has an unhybridized p orbital, which can form a pi bond by overlapping side to side with a p orbital of an adjacent atom (C, N, or O) to which it is already joined by a sigma bond; the pi and sigma bond together constitutes a double bond. sp-hybridized carbon has two unhybridized p-orbitals and forms a triple bond with another C or N, made up of a sigma and two pi bonds.
Rule 2 of the VSEPR Theory
2. Three pairs of electrons are always 120 degrees apart (Trigonal Planar)
Rule 1 of the VSEPR Theory
1. Two pairs of electrons on central atom are always 180 degrees apart (Linear)
Step 1 for Drawing Lewis Structure
1. Add all valence electrons of all atoms.
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