Chemistry unit 3

valence-shell electron-pair repulsion (VSEPR)

a model that says valence electrons will repel each other, so molecules will form 3-Dimensional shapes with the greatest distance between electrons

electron domain

a lone pair or set of bonds. Considered from the central atom when using the VSEPR model

electron-domain geometry

the arrangement of electron domains around the central atom

molecular geometry

the arrangement of bonded atoms

bond angle

the angle between two adjacent bonds

what is the bond angle of a molecule with 2 electron domains and no lone pairs?

180 degrees

what is the bond angle of a molecule with 3 electron domains and no lone pairs

120 degrees

what is the bond angle of a molecule with four electron domains and no lone pairs

109.5 degrees

what are the bond angles of a molecule with five electron domains and no lone pairs

90 degrees and 120 degrees

what is the bond angle of a molecule with six electron domains and no lone pairs

90 degrees

equatorial

the 3 bonds on the bond axis in a trigonal bipyramidal molecule

axial

the 2 bonds perpendicular to the bond axis in a trigonal bipyramidal molecule

what is the shape of a molecule with 2 electron domains and no lone pairs

linear

what is the shape of a molecule with three electron domains and no lone pairs

trigonal planar

what is the shape of a molecule with four electron domains and no lone pairs

tetrahedral

what is the shape of a molecule with five electron domains and no lone pairs

trigonal bipyramidal

what is the shape of a molecule with six electron domains and no lone pairs

octahedral

what is the shape of a molecule with three electron domains and one lone pair?

bent

what is the shape of a molecule with four electron domains and one lone pair

trigonal pyramidal

what is the shape of a molecule with four electron domains and two lone pairs

bent

what is the shape of a molecule with five electron domains and one lone pair

see-saw shaped

what is the shape of a molecule with five electron domains and two lone pairs

T-shaped

what is the shape of a molecule with five electron domains and three lone pairs

linear

what is the shape of a molecule with six electrons domains and one lone pair

square pyramidal

what is the shape of a molecule with six electron domains and two lone pairs

square planar

structural isomers

molecules that have the same chemical formula but different molecular arrangements

intermolecular forces

attractive force between neighboring molecules

dipole-dipole interactions

attractive forces between polar molecules due to polarity

hydrogen bonding

dipole-dipole interactions between hydrogen atoms involved in polar covalent bonds

instantaneous dipole

a temporary dipole caused by electrons moving around atoms

dispersion forces

a chain reaction of induced dipoles after the formation of an instantaneous dipole

polarization

the ability of a molecule to have induced dipoles

ion-dipole interactions

interactions between ions and polar molecules

valence bond theory

atoms covalently share electrons when their orbitals overlap

hybridization

mixing of atomic orbitals

hybrid orbitals

a combination of s, p, d, or f orbitals

sigma bonds

bonds resulting from the overlap of orbitals in between two electrons. (1st bond)

pi bonds

bonds that form from the sideways overlap between p orbitals (2nd and 3rd bonds)

molecular orbital theory

orbitals formed during molecular bonding are shared by the entire molecule

bonding molecular orbital

a molecular orbital that is lower in energy than the orbitals paired to produce it. Pulls nuclei toward each other

antibonding orbital

a molecular orbital that is higher in energy than the orbitals paired to produce it. Pulls nuclei away from each other

delocalized

bonds that move around the entire structure of a molecule with multiple resonance structures

localized

bonds confined between two atoms in a molecule

bond order equation

(#of bonding orbitals - #of antibonding orbitals)/2

octet rule

Atoms will gain, lose, or share electrons to become isoelectronic with a noble gas. Beryllium and Boron don’t follow the octet rule.

lone pairs

pairs of valence electrons that are not involved in covalent bonding

single bond

when one pair of electrons is shared between atoms

double bond

when two pairs of electrons are shared between atoms

triple bond

when three pairs of electrons are shared between atoms

bond length

distance between the nuclei of covalently bonded atoms

polar covalent bonds

bonds where electrons are not shared equally, creating partial positive and negative charges

electronegativity

the ability of an atom to draw shared electrons to itself. Increases left to right and decreases top to bottom on the periodic table

What difference in electronegativity corresponds to a nonpolar bond?

<0.5

What difference in electronegativity corresponds to a polar bond?

0.5<…<2.0

What difference in electronegativity corresponds to an ionic bond

2.0<

dipole momement

quantitative measure of polarity

dipole moment equation

M=Qxr

Debye unit equation

3.34×10^-30C(m)

Coulombs equation

1e=1.6×10^-19

Formal Charge

the valence electrons an element has in a Lewis structure minus the electrons assigned to it on the periodic table

resonance structure

one of multiple equally valid Lewis structures for a molecule

coordinate covalent bond

a covalent bond where one atom shares both electrons

Lewis base

an atom that donates two electrons in a coordinate covalent bond

Lewis acid

an atom that accepts two electrons in a coordinate covalent bond

free radical

highly reactive molecules with an odd number of electrons

expanded octets

additional octets formed using electrons from the d subshell