Test 4 Flashcards
VSEPR stands for
Valence shell electron pair repulsion
When it comes to repulsion list the 3 pair groupings from most repulsive to least
(lone pair, lone pair) > (lone pair, bond pair) > (bond pair, bond pair)
2 electron groups
linear, 180
3 electron groups
trigonal planer, 120
3 electron groups - 1 lone pair
bent, <120
4 electron groups
tetrahetral, 109.5
4 electron groups - 1 lone pair
trigonal pyramidal, <109.5
4 electron groups - 2 lone pair
bent, <109.5
5 electron groups
trigonal bypyramidal, 90,120
5 electron groups - 1 lone pair
seesaw, <120
5 electron groups - 2 lone pair
t-shaped, <90
5 electron groups - 3 lone pair
linear, 180
6 electron groups
octahedral, 90
6 electron groups - 1 lone pair
square pyramidal, <90
6 electron groups - 2 lone pair
square planar
Trend in atomic radius
Increases from top right to bottom left
nonbonding atomic radius is the same as this
van der Waals radius
bonding atomic radius is the same as this
covalent radius
How is the atomic radius measured in metals and nonmetals
Metals- 1/2 the distance between two of the atoms next to each other in a crystal of metal
nonmetals- 1/2 the distance between two of the atoms bonded togeather
The atomic radius is determined by this
a set of average bonding radii
Which is larger atomic radius or van der Waals radius
Atomic radius < van der Waals radius
Atomic radius is found by doing this
adding each atomic radius of a molecule to find the molecules atomic radius
Formula for finding effective nuclear charge
effective nuclear charge = actual nuclear charge - charge screened by the other electrons
Which group of elements atomic radius stays relatively consistant
transition metals
What is the exception to the rule when removing electrons to form a cation
In transition metals you remove the greatest N value shell first, even if it is not the reverse order
Paramagnetic, what is it, and how does it react in a magnetic field
an atom or ion that contains unpaired electrons, attracted to an external magnetic field
diamagnetic, what is it, and how does it react in a magnetic field
an atom or ion that contains no unpaired electrons, repelled by an external magnetic field
Trends in cations, and anions
Cations are much smaller than their respective atom, and anions are much larger than their respective atom
What is ionization energy
energy required to remove an electron from an atom or ion in its gasous state
What is the sign of ionization energy and why
positive, because it always takes energy to remove an electron
Trend in ionization energy
Increases from bottom left to top right
Are there any exceptions to the ionization energy trend, and if so what are they
Yes, half filled shells have lower then expected ionization energy
Where do jumps in ionization energy occur
when removing electrons past a stable electron core
What is electron affinity
energy change associated with the gaining of an electron by the atom in the gaseus state
What is the sign of electron affinity and why
usually, but not always negative. because an atom or ion usually release energy when it gains and electron
trend in electron affinity
become more negative as you move from the left to right
Are there any exceptions to the electron affinity trend, and if so what is it
yes, half filled shells are lower then the trend, and almost half filled shells are higher then the trend
trend in metalic character
Increases from top right to bottom left
What is the best reason to discribe why chemical bonds form
because they lower the potential energy between the charged particals that compose atoms
Three types of bonds
Ionic, covalent, metallic
metal to nonmetal form
ionic
nonmetal to nonmetal
covalent
metal to metal
metallic
Born-haber cycle formula is used for these types of bonds
ionic
Born-Haber cycle formula is
dH_f = sub + IE + BE + EA + lat
Trends in lattice energy
as the ionic radii increase as we move down the column, the ions cannot get as close to eachother and therefore do not release as much energy when the lattice forms
This happens to lattice energies as atomic radii increase and decrease
as ionic radii increase lattice energy becomes less exothermic(less negative),
as ionic radii decrease lattice energy becomes more exothermic ( more negative)
T/F: Electrons are always equally shared
F, the more electronegative atom uneually shares the electrons
This type of bond is between pure covalent and ionic
polar covalent
trend in electronegativty
increases from bottom left to top right
covalent bonds are classified by an electronegativity difference of this range, and do this with their electrons
0 - .4 , equally share
polar covalent bonds are classified by and electronegativity difference of this range, and do this with their electrons
.4 - 2, unequally share
Ionic bonds are classigied by an electronegativity difference of this range, and do this with their electrons
2+ , transfer
(4) Steps for writing Lewis structure for molecular compounds
- Write the correct skeletal structure for the molecule\
- calculate the total number of electrons
- distribute the electrons among the atoms, giving octets to as many atoms as possible
- If any atoms lack octets, form double/triple bonds as necessary to give them octets
For polyatomic ions do this in your lewis structures
- put it in brackets
2. add/subtract the proper amount of electrons for the given ionic charge
How to find the formal charge
formal charge = number of valence electrons originally for the atom - (total lone pair electrons + 1/2 bonded pair electrons)
Odd electron species include
free radicals, incomplete octets, expanded octets
Free radicals have this
and odd number of electrons and are generally unstable
Some atoms that form incomplete octets include
Boron {B}, Beryllium {Be}
Atoms that may form expanded octets
Atoms that are at N>=3 may have expanded octets
Bond energy formula
dH_rxn = sum(d)H_bonds broken + sum(d)H_bonds formed
The sign of broken bonds, and the sign of formed bonds
broken bonds are positive, and formed bonds are negative
Exothermic reactions occur when
weak bonds break and strong bonds form
Endothermic reactions occur when
weak bonds form and strong bonds break
