Unit 4- Chemical Bonding

intramolecular force

chemical bonds that hold atoms together within a molecule

bond

force that holds groups of two or more atoms together and makes them function as a unit

bond energy

energy required to break a bond

bond strength

what does bond energy tell us?

to achieve 8 electrons

why do stable elements form bonds?

metal

forms bonds because it wants to achieve the electron configuration for the noble gas before it

nonmetals

forms bonds because it wants to achieve the electron configuration for the noble gas after it

ionic bonds

form by atoms transferring electrons, strongest bonds

metal

in ionic bonds, cation=

nonmetal/metalloid

in ionic bonds, anions=

a metal and a nonmetal

in ionic bonds, it always occurs between…

ionic compound properties

do not consist of molecules, crystal lattice, solid at room temp, brittle, high boiling and melting points, can conduct electricity when dissolved in water

crystal lattice

huge network of positive and negative ions

ionic compounds

only compound that can conduct electricity when dissolved in water

covalent bonds

form by atoms sharing electrons

nonmetals and metalloids

covalent bonds always occur between…

covalent compound properties

do consist of molecules, gas or liquid at room temp, soft if solid, low melting and boiling points, cannot conduct electricity, diatomic molecules

covalent compounds

only compound that can’t conduct electricity and has lowest melting and boiling points

diatomic molecules

made up of 2 atoms

BrINClHOF

diatomic molecules

metallic bonds

form by metal cation electrons moving freely between atoms, forms a sea of electrons- electrons become delocalized and are shared by all metal cations

metallic compound properties

solid at room temp, malleable, ductile, high boiling and melting points, do conduct heat and electricity as a solid sometimes, luster

intermolecular forces

the attractive and repulsive forces that arise between the molecules of a substance

lewis structure

representation of a covalent molecule/compound, shows how the valence electrons are arranged among the atoms in the molecule

transitional metals

what do not form covalent bonds?

octet rule

surrounded by 8 ve, obtained by gaining, losing, or sharing electrons

duet rule

2 ve

expanded octet

elements in period 3 and lower can have more than 8 ve

bonding pair

electrons shared with another atom

single bond

involves two atoms sharing one pair

double bond

involves two atoms sharing two pairs

triple bond

involves two atoms sharing three pairs

resonance

more than one lewis structure can be drawn for the molecule

lone pairs

paired electrons on the central atom, not involved in bonding, repel more strongly them electrons in bonds, reduced angle between atoms

chemical and physical properties

what do three dimensional arrangements help to account for?

flat

molecules and polyatomic ions are not all…

vsepr model

occurs around a central atom

as far away from each other as possible

lone pairs like to be…

minimize repulsive forces between electrons

what is the goal of lone pairs?

electron domain

an area of electron concentration

one domain

double and triple bonds count as…

bonded domain

area that a single, double, and/or triple bond occupies

linear

2 bonded domains, 2 electron domains on central atom, 0 lone pairs

trigonal planar

three bonded domain, 3 electron domains on central atom, 0 lone pairs

tetrahedral

four bonded domains, 4 electron domains in central atom, 0 lone pairs

bent

combination of two bonded domains, 1-2 lone pairs, 3 electron domains in central atom

trigonal pyramidal

4 electron domain on central atom, 3 bonded domains, 1 lone pair, 107 degrees

lone pairs

repel more strongly than bonded domains

bond angles

the repulsion of electrons creates…

polar covalent bonding

unequal sharing of electrons, positive end attracted to negative end

nonpolar covalent bonding

equal sharing of electrons, all areas of the molecule are neutral

electronegativity

relative ability of an atom in a molecule to attract shared electrons to itself

the higher the electronegativity

the closer the shared electrons tend to be to that atom when it forms a bond

born polarity, vsepr, symmetry

3 factors that affect molecular polarity is…

polar molecule

contains a dipole moment, dipole moments do not fully cancel

nonpolar molecule

dipole moments cancel eachother

dipole moment

occurs when there is a distance between opposite charges, has a center of positive and negative charge, comes from differences in electronegativity, the larger the difference, the greater the effect

covalent molecules

intermolecular forces only apply to…

intramolecular forces, intermolecular

… are strong than…

LDFs, dipole-dipole, hydrogen bonding

types if intermolecular forces

results of strong forces

high boiling point, melting point, surface tension, and viscosity

LDFs

very weak forces, occurs in all molecules/atoms, caused by uneven distribution of electrons, only force that exists in nonpolar and noble gasses, increases when more electrons

instantaneous dipole

uneven distribution of electrons, results in brief polarity

dipole-dipole

only present in polar molecules, polar molecules orient themselves so that + and - are closer to each other

hydrogen bonding

types of dipole-dipole attraction, not a chemical bond

hydrogen

what is the strongest IMF

HN, HO, or HF

it is hydrogen bonding if a molecule contains…

0-0.3

nonpolar covalent

0.3-1.7

polar covalent

>1.7

ionic

180

linear bond angle:

120

trigonal planar bond angle:

<120

bent bond angle:

107

trigonal pyramid bond angle:

109.5

tetrahedral bond angle: