Chapter 7: Chemical Bonding and Molecular Geometry

ionic bonds

electrostatic forces of attraction between oppositely charged cations and anions

covalent bonds

a mutual attraction / sharing of electrons between two non-metals

polar covalent bonds

unequal distribution of electrons (0.4-1.8)

pure covalent bonds

electrons shared with an equal probability of being near each nucleus (0-0.4)

electronegativity

determines whether a bond is polar or non-polar

Pauling Scale

measure of electronegativity

Lewis symbol

an elemental symbol surrounded by 1 dot for each valence electron

Lewis structures

drawings that show the formation of covalent bonds

lone pairs

pairs of electrons not used in bonding

octet rule

rule that states that all main group atoms wish to have a valence shell of 8 electrons

hypervalent molecules

when valence electrons exceed the octet rule

formal charge

the hypothetical charge an atom would have if we redistributed the electrons evenly (# of valence electrons - # of lone pairs - half of the bonding electrons)

molecular structure

the arrangement of atoms in a molecule of an ion

resonance

2 or more lewis structures that can be written with the same arrangement

bond strength

how strongly an atom is joined to another atom

bond energy

energy required to break 1 mole of gaseous molecules

lattice energy

the energy required to separate 1 mol of solid into its component gaseous ions

bond angle

the angle between 2 bonds that include a common ion

bond distance

the distance between the nuclei of 2 bonded atoms along the straight line joining the nuclei (measured in Ångstroms)

VSEPR theory

enables us to predict the molecular structure ond the approximate bond angles

linear

bond angle 180°

trigonal planar

bond angle 120°

tetrahedral

bond angle 109.5°

trigonal bipyramidal

bond angle 120° and 90°

octahedral

bond angle 90° or 180°

bond dipole moment

the separation of partial negative and partial positive charges

dipole moment

the extent of teh net charge separation of the whole molecule