Chem Exam Ii

Front 1

molecular mass

Back 1

sum of atomic masses of all atoms in molecule of substance

Front 2

mole

Back 2

quantity of a given substance that contains as many molecules as of atoms in exactly 12g of carbon12

Front 3

molar mass

Back 3

mass of one mole of a substance

Front 4

avogadro's number

Back 4

number of atoms in a mole

Front 5

percent composition

Back 5

mass percentage of each element in compound

Front 6

empirical formula

Back 6

simplist formula, written with smallest integers possible

Front 7

molecular formula

Back 7

multiple of empirical formula

Front 8

VSEPR

Back 8

Predicts shapes of molecules and ions
Assumes e- pars kept far away from each other
o Minimizes repulsion
Direction in space gives molecular geometry

localized bonding models

Front 9

'rules' for vsepr

Back 9

lewis dot structure
any resonance
sum of e- paris around central
minimize e- pair repulsion (lone pairs require more room)

Front 10

dipole moment

Back 10

quantitative measure of degree of charge separation in molecule

vector quantity ( magnitude and direction )

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cis

Back 11

molec same side, dipole likely

higher boiling point

Front 12

trans

Back 12

molec opp side, unlikely dipole

lower boiling point

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intermolecular force

Back 13

in liquid polar molecules orient so + end attracted to - end
increases energy required for liquid to break
increases boiling point

Front 14

two theories stemming from quantum mechanics

Back 14

valence bond theory
molecular orbital theory

Front 15

valence bond theory

Back 15

- an orbital onone atoms occupys portion of same region of space as orbital on another atom, orbitals overlap
- total number of electrons in both orbitals no more than 2

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hybrid orbitals

Back 16

apart of valence bond theory
describe bonding, obtained by taking combo of atomic orbitals from isolated atoms
number hybrid formed always = number atomic used

Front 17

Sigma bond

Back 17

cylindrical shape about bond axis, when two s orbitals overlap or other (ex p) does so along their axis ( imaginary line connecting nuclei

Front 18

pi bond

Back 18

electon distribution above and below bond axis, sidways overlap of two p orbitals
o When two parallel orbitals are still available after strong sigma formed

Front 19

Molecular orbital theory:

Back 19

which may spread over several atoms or the entire moleule

Structure of molecules similar to atoms

Each orbital has definite energy, ground state, fills lowest energy first

better than lewis bc combines atomic orbitals, molecular orbital formed 'covers' other atoms

limited to diatomic

Front 20

bonding orbitals

Back 20

molecular obitals that are concentrated in regions btwn nuclei

less energy

Front 21

antibonding

Back 21

zero values in region between nuclei

more energy

Front 22

Molecular orbital theory:

Back 22

which may spread over several atoms or the entire moleule

Structure of molecules similar to atoms

Each orbital has definite energy, ground state, fills lowest energy first

better than lewis bc combines atomic orbitals, molecular orbital formed 'covers' other atoms

limited to diatomic

Front 23

bond order

Back 23

molecular orbital theory

1/2 diff of [ bonded electrons - antibonded elecectrons]

Front 24

bonding orbitals

Back 24

molecular obitals that are concentrated in regions btwn nuclei

less energy

Front 25

antibonding

Back 25

zero values in region between nuclei

more energy

Front 26

hunds rule

Back 26

lowest energy arrangement of electrons in subshell obtained by putting electrons into separate orbitals of subshell w/ same spin before pairing electrons

Front 27

aufbau principle

Back 27

scheme used to reproduc electron configuration of ground states of atoms by successively filling subshells w/ electrons in specific order

Front 28

bond order

Back 28

molecular orbital theory

1/2 diff of [ bonded electrons - antibonded elecectrons]

Front 29

hunds rule

Back 29

lowest energy arrangement of electrons in subshell obtained by putting electrons into separate orbitals of subshell w/ same spin before pairing electrons

Front 30

pauli exclusion principle

Back 30

no tow electrons in atom can have same four quantum numbers

Front 31

aufbau principle

Back 31

scheme used to reproduc electron configuration of ground states of atoms by successively filling subshells w/ electrons in specific order

Front 32

pauli exclusion principle

Back 32

no tow electrons in atom can have same four quantum numbers

Front 33

lewis dot shortcomings

Back 33

assume electrons localized
dont deal w/ unpaired electrons
dont provide good information about bond energies

Front 34

ionic bond

Back 34

chem bond formed by attraction between + and - ions

each new ion often more stable than molec before

Front 35

elements for octet rule

Back 35

c, n, o, f

fails for h, b, and odd electron species, many w/ z> 10

Front 36

coulumbs law

Back 36

determines energy released when ions bond

attraction of opp charged ions

larger interaction of = greater melting point

Front 37

lattice energy

Back 37

change in energy from ionic solid separated to ions of gas phase

solid to gas = + value
gas to solid = - value

Front 38

melting points

Back 38

depend on strength of interaction between atoms or ions
ionic solids have high melting points because strong interaction between ions , more energy to vibrate and bonds and pull to farther distances

Front 39

transition metals & valence eletrons

Back 39

in ionic compounds, lose ns electrons first
then (n-1)d

because 2 lost are highest energy s electrons from atom

Front 40

ionic radius

Back 40

spherical region around nucleus which electrons are likely to be found

increases down column because of addition of electron shells

increases across table

Front 41

anion radii vs cation

Back 41

anion larger bc greater e- repulsion

Front 42

isoelectric

Back 42

same number and configuration of electrons

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covalent bond:

Back 43

chemical bond by sharign of electrons between atoms

Front 44

valence bond theory

Back 44

assume orbitals stay intact
valence only
bodn formed by overlatp of atomic orbitals

lewis dot

Front 45

mo theory

Back 45

atomic orbitals combine to form new molecular orbitals that cover entire molecue

atomic orbitals no longer exist once molecular orbitals formed
considers all electrons

Front 46

ionic nomenclature

Back 46

roman numerals, ide

Front 47

ionization energy

Back 47

min energy needed to remove electron

decreases as becomes easier to remove electron

Front 48

electron affinity

Back 48

enery change for process of adding electron

large negative indicates stable NEGATIVE ion FORMED ( large negative means wants badly)

small negative, doesnt want it