Chem Flashcards
How many cm^3 in a litre?
1000
How many litres in a m^3?
1000
What are the 7 rules for assigning oxidation states? (in order of precedence)
1) any element in its standard state is 0
2) the sum of the oxidation states in a molecule must equal the molecule’s charge
3) group 1 metals have +1, group 2 metals +2
4) fluorine is -1
5) H is +1 when bound to something more electronegative than C, -1 when bound to some less electronegative and 0 when bound to C
6) oxygen is -2
7) the rest of the halogens have -1 and atoms in the oxygen family have -2
What are isotopes?
two of the same element that differ in their number of neutrons
How are frequency and wavelength related to photon energy?
E = hf = hc/wavelength
directly proportional to frequency, indirectly proportional to wavelength
Describe the Bohr model of the atom
electrons orbit the nucleus in circular paths
electrons with greater energy orbit at greater distances
electrons have quantized energy states
What model helped explain that emission spectra are line spectra and not continuous spectra?
Bohr model
What is a Bohr atom?
an atom that contains only one electron
How would the energy emitted from an electron dropping from n=4 to n=3 compare to that of an electron dropping from n=3 to n=2?
n=4 to n=3 would have LESS energy released
i.e. the differences get smaller between higher levels
What regions of the electromagnetic spectrum can be emitted when an electron transitions?
UV, visible, infrared
What shape are s orbitals? How many electrons can they hold?
spherical
can hold 2 electrons
What shape are p orbitals? How many electrons can they hold?
sort of like a dumbbell
can hold 6 electrons
How many electrons can d and f subshells hold?
d can hold 10 electrons
f can hold 14 electrons
What is the Aufbau principle?
electrons occupy the lowest energy orbitals available
What is Hund’s rule?
electrons in the same subshell occupy available orbitals singly before pairing up
What is the Pauli exclusion principle?
there can be no more than 2 electrons in any given orbital
What does diamagnetic mean?
all electrons are spin-paired
there is no net magnetic field
atom will be repelled by an externally produced magnetic field
What does paramagnetic mean?
electrons are NOT all spin-paired
atom will be attracted to an externally produced magnetic field
What is a period? Group/family?
period = horizontal row across the periodic table group/family = vertical column
What can happen that gives electron configurations different from what you would expect?
if you can have d5 or d10 i.e. a half or completely full shell an electron will be promoted from s2 to do so
What does isoelectronic mean?
when two atoms have the same electron configuration
How are electrons lost from orbitals?
always from the highest energy (highest n) first
ie 4s2 before 3d
What is the excited state of an atom?
when electron configuration isn’t what is predicted but still follows the rules
Which group are the alkali metals?
group 1
Which group are the alkaline earth metals?
group 2
Name the 7 metalloids
boron (B) silicon (S) Ge As Sb Te Po
What is nuclear shielding/the shielding effect?
each filled shell between the nucleus and the valence electrons shields the valence electrons from the full effect of the positively charged protons in the nucleus
What is the result of nuclear shielding?
effective nuclear charge
valence electrons experience an effective reduction in the positive elementary charge
What are the trends for atomic radius?
decreases across a period
increases down a group
How do ions vary in size?
cations
What is ionization energy?
the amount of energy necessary to remove the least tightly bound electron from an atom
What are the trends for ionization energy?
increases across a period
increases up a group
How does first ionization energy compare to second?
second will always be greater
What is electron affinity?
the energy associated with the addition of an electron to an atom
if energy is released affinity is negative, if it is required affinity is positive
(negative is favoured)
What are the trends for electron affinity?
becomes more negative as you go across a period or up a group
(decreases to the right and up)
What is electronegativity?
a measure of an atom’s ability to pull electrons to itself when it forms a covalent bond
What are the trends for electronegativity? Give specifically the order of the 9 most electronegative elements
increases across a period
increases up a group
F > O > N > Cl > Br > I > S > C ~ H
What are the trends for acidity?
increases across a period
increases down a group
What are the 3 types of intramolecular forces?
covalent bonds
ionic bonds
metallic bonds
What is a coordinate covalent bond?
One atom donates both electrons in a bond
ie hemoglobin and iron
What affects ionic bond strength? Which trend is most important?
1) increasing charge magnitude increases bond strength (most important)
2) decreasing ionic radius increases bind strength
What are some properties of metals? (with metallic bonds)
sea of delocalized valence electrons between nuclei
conduct heat and electricity
malleable
ductile
When making a Lewis dot diagram for a transition metal what is different about it?
you don’t include valence electrons in the d orbitals
Which elements does the octet rule apply to?
2nd row
B, C, N, O, F, Ne
What hybridization is H?
always just s because it can’r hybridize
What is the difference between orbital geometry and shape?
orbital geometry is determined by the # of electron groups
shape is determined only by the bonds
What are the 3 intermolecular forces?
London Dispersion Forces (LDFs)
Dipole-dipole
H bonding
Rank the types of intermolecular forces from strongest to weakest
H bonding > dipole-dipole > LDFs
What are van der Waals forces?
includes H bonding, dipole-dipole and LDFs, but a lot of people call LDFs van der Waals
Describe London Dispersion Forces
present between all molecules
weakest intermolecular force
caused by instantaneous dipoles
increase with increasing molar mass
Describe dipole-dipole forces
only happen between polar molecules
permanent dipole is attracted to another
What is needed for an H-bond?
H covalently bound to F, O or N
Lone pair of electrons on F, O or N
What id homiletic bond cleavage?
one electron of the bond being broken goes to each fragment of the molecule (forms two radicals)
What is heterolytic bond cleavage?
both electrons of the bond being broken end up on the same atom
What is bond dissociation energy?
the energy required to break a bond homolytically
What is the teen between bond length and bond dissociation energy?
the higher the bond order (#of bonds between two atoms), the shorter and stronger the bond is
What are bond lengths measured in?
angstroms, A
1 x 10^-10m
How does s character related to the length of a bond?
the greater the s character in hybrid orbitals, the shorter the bond i.e. sp-sp bonds are shorter than sp-sp3
What is the relationship between intermolecular forces and melting point?
higher IMFs = higher melting point
need to weaken IMFs in order to melt something
What is the relationship between intermolecular forces and boiling point
higher IMFs = higher boiling point
need to break all IMFs in order for boiling to occur
What is vapour pressure? How is it related to intermolecular forces?
the pressure of a gas that has evaporated from liquid
higher IMFs = LOW vapour pressure
What does volatile mean in terms of intermolecular forces?
low intermolecular forces, high vapour pressure
What is the relationship between viscosity and intermolecular forces?
high IMFs = high resistance = high viscosity
What is a network solid?
a solid in which atoms are connected in a lattice of covalent bonds
there are only intramolecular forces
very strong, tend to be very hard solids at room temp i.e. diamond
What is a metallic solid?
a metal
covalently bound lattice of nuclei and their inner shell electrons surrounded by a “sea” of electrons
vary widely in strength, but most are solid at room temp
What is a molecular solid?
crystal lattice of molecules held together by intermolecular interactions
often liquids or gases at room temp
What is the zeroth law of thermodynamics?
When systems are in thermal equilibrium, they have the same temperature
If two bodies of different temperatures are brought into contact with one another, heat will flow from the body with the higher temperature to the body with the lower temperature
What is the first law of thermodynamics?
energy cannot be created or destroyed, only transformed
also, work can be put into a system to increase its overall energy (may or may not occur with a temperature change)
Describe enthalpy when bonds are broken and formed
when bonds are formed energy is released (H0), endothermic
What is delta H?
“heat of reaction”
What are the 3 ways to calculate delta H (heat of reaction)?
1) using heats of formation
(sum of n x delta H products) - (sum of n x delta H reactants)
2) Hess’s law of heat summation
enthalpy is a state function, energy absorbed or released by overall reaction is the same as the sum of the individual steps
3) Summation of bond enthalpies (bond dissociation energies)
(sum BDEbroken) - (sum BDEformed)
What is is a heat of formation?
the change in energy associated with forming 1 mol of a compound from its elements in their standard states under standard conditions