GC1 Exam II

ionic bonds

bonds that form when an electron is transferred between a metal and a non-metal

ionic compounds

a compound that is composed of cations and anions

covalent bonds

bonds that form when an electron is shared between two non-metals

molecular compounds

a compound that is composed of covalently bonded non-metals

empirical formula

a formula that indicates the relative number of atoms present in each element within a compound

molecular formula

a formula that indicates the actual number of atoms present in each element in a molecule within a compound

structural formula

a formula that shows how atoms in a molecule are connected/bonded to each other

lewis symbol

a symbol that represents valence electrons of main group elements as dots that surround the elements abbreviation

octet

atoms that have a full outer principle level with 8 valence electrons

duet

atoms that have a full outer principle level with only 2 valence electrons

lattice E

the energy released when gaseous ions form ionic compounds

how to find the lattice E

1. multiply the charges of each ion

2. take the absolute value of the product

3. divide the product by the distance between the ions

as as the charge of the ions increases what happens to the lattice E?

the lattice E increases

as the distance between the ions increases what happens to the lattice E?

the lattice E decreases

characteristics of ionic compounds

1. high melting/boiling points

2. non-conductors when solid

3. conductors when liquid

4. bonds are non-directional

why do ionic compounds have high melting/boiling points?

ionic compounds are composed of strong forces that require a significant amount of heat to break

why are ionic compounds poor conductors of electricity when solid?

the electrons in solid ionic compounds are not moving freely in an electrical current

why are ionic compounds good conductors of electricity when liquid?

the electrons in liquid ionic compounds are moving freely in an electric current since the ions have dissolved

why are ionic compound bonds non directional?

any cation can pair with any anion

how to find the formula of an ionic compound

1. find the symbol and charge of the metal + the symbol and charge of the non-metal

2. adjust the subscripts so that the cations = anions

binary ionic compounds

compounds that are made up of a metal and a non-metal elements

binary compound formula

name of cation + [base name of anion + ide]

transition metal compound rule

a transition metal must be followed a roman numeral that indicates which charge is present

oxyanions

a polyatomic anion that contains oxygen paired with another element

oxyanion ite meaning

between two oxyanions the one that has less oxygen will end in ite

oxyanion ate meaning

between two oxyanions the one that has more oxygen will end in ate

oxyanion hypo meaning

between multiple oxyanions the one that has the least amount of oxygen will begin with hypo

oxyanion per meaning

between multiple oxyanions the one that has the most amount of oxygen will begin with per

hydrates

ionic compounds that contain a specific number of water molecules associated with each formula unit

hemi prefix

½

mono prefix

1

di prefix

2

tri prefix

3

tetra prefix

4

penta prefix

5

hexa prefix

6

hepta prefix

7

octa prefix

8

nona prefix

9

deca prefix

10

bonding pair

a pair of electrons shared between two atoms

lone pair

a pair of electrons that are associated with only one atom

intermolecular forces

interactions between molecules

intramolecular forces

interactions within a molecule

molecular compound characteristics

1. low melting/boiling point

2. bonds are directional

why do molecular compounds have low melting/boiling points?

the intermolecular bonds that hold molecules together are weak and easy to break

why are molecular compound bonds directional?

each bond must pair with a specific set of atoms

binary molecular compounds

compounds that are made up of two non-metals

binary molecular compound formula

[prefix + name of 1st non metal] + [prefix + base name of 2nd non-metal + ide]

formula mass

the sum of the atomic masses of all the atoms within a compound

mass percent

a number that represents how much of an element is present within a compound

combustion analysis

a method that can determine the empirical formula of a compound that is made up of C and H

how to find the empirical formula from combustion analysis

1. find the moles of each element in the compound

2. divide by the smallest mole number

3. multiply to get the nearest whole number if needed

hydrocarbons

the simpliest organic compounds that are composed of C and H

electronegativity

the ability of an atom to attract electrons towards itself

polar covalent bonds

covalent bonds that unequally share electrons due to differences in electronegativity

non-polar covalent bonds

covalent bonds that equally share electrons due to similarities in electronegativity

dipole moment

occurs whenever a positive and negative charge separate

percent ionic character

the ratio of a bonds actual dipole moment to the dipole moment it would have if the electron were completely transferred from one atom to the other

5 steps for writing lewis structures

1. write the skeletal structure

2. calculate the total # of valence electrons of each atom

3. place bonding pairs around the central

4. place lone pairs around the terminals

5. form double or triple bonds to give the central 8 electrons

polyatomic lewis structure rules

subtract 1 electron for every positive charge and add 1 electron for every negative charge

resonance structures

lewis structures that have the same skeletal formula but different electron arrangements

formal charge

the charge an atom would have if all of its bonding electrons were shared equally

formula change equation

# of valence electrons = [ # of non-bonding electrons + ½(# of bonding electrons) ]

4 rules of formula charge

1. the sum of all formula charges in a neutral molecule must be 0

2. the sum of all charges in an ion must equal the charge of the ion

3. small or zero formal charges on individual atoms are better than large ones charges

4. negative formula charge will reside on the most electronegative atom

free radicals

unstable and reactive molecules/ions that contain an odd number of valence electrons in their lewis structure

incomplete octets

molecules/ions with less than 8 electrons

expanded octets

molecule/ions with more than 8 valence electrons

why are expanded octets expanded?

to lower their formal charge

bond E

the E required to break 1 mol of a bond in the gas phase (endothermic)

VSEPR

a model that can determine a molecules geometry based on the repulsions between electron groups

electron groups

lone pairs, single bonds, multiple bonds, or lone electrons

5 molecular geometries

1. linear

2. trigonal planar

3. tetrahedral

4. trigonal by pyramidal

5. octahedral

linear geometry

2 electron groups

180° angles

trigonal planar geometry

3 electron groups

120° angles

tetrahedral geometry

4 electron groups

109.5° angle

trigonal pyramidal geometry

3 bonding pairs

1 lone pair

trigonal bipyramidal geometry

5 electron groups

120° angle

90° angle

equatorial groups

groups located in the trigonal plane (lay flat)

axial groups

groups that lay on either side of the trigonal plane

2 types of trigonal bipyramidal geometry

1. seesaw

2. T-shaped

seesaw geometry

4 bonding pairs

1 lone pair

T-shaped geometry

3 bonding pairs

2 lone pairs

octahedral geometry

6 electron groups

90° angles

2 types of octahedral geometry

1. square pyramidal

2. square planar

square pyramidal

5 bonding pairs

1 lone pair

square planar

3 bonding pairs

2 lone pairs

electron group repulsion ranking

lone-lone > lone-bonding > bonding-bonding

the greater the repulsion = the smaller the bond

polar polyatomic molecule

a molecule whose polar bonds have a dipole moment sum greater than 0

non-polar polyatomic molecule

a molecule whose polar bonds have dipole moment sum equal to 0

valence bond theory

chemical bonds form when half filled atomic orbitals overlap

hybrid orbitals

orbitals that correspond to the actual distribution of electrons in chemically bonded atoms

5 types of hybrid orbitals

1. sp

2. sp2

3. sp3

4. sp3d

5. sp3d2

geometry and angle of sp

1. linear

2. 180°

geometry and angle of sp2

1. trigonal planar

2. 120°

geometry and angle of sp3

1. tetrahedral

2. 109.5°

geometry and angles of sp3d

1. trigonal bipyramidal

2. 120° and 90°

geometry and angle of sp3d2

1. octahedral

2. 90°

sigma bonds

bonds that form when hybrid orbitals overlap head-on

pi bonds

bonds that form when unhybridized p orbitals overlap side to side