Gen Chem Flashcards
What are isotopes?
Same elements with the same atomic number (protons) and chemical properties but different number of neutrons (mass number)
What do valence electrons determine?
Chemical properties of that molecule
VE’s are also the most easily removed and most available for bonding
Electrons: lowest mass
Protons: moderate mass
Neutrons: most mass
Atomic mass vs. atomic weight?
Atomic mass: roughly equal to the mass number in amu
Atomic weight: weighted average of isotopes (as most all elements exist as isotopes)
What is important in the Bohr model about electron energy levels?
As electrons rise in energy level they absorb light, become excited, have higher potential, and become more distant from the nucleus
If enough energy is transferred electrons can move to an excited state (beyond ground state of n=1)
Excitation is brief and the return to ground state is associated w/ photon emission
Instead of the Bohr model where do electrons really exist?
In orbitals or regions in space b/c of electron-electron repulsion
What is the Heisenberg Uncertainty principle?
It is impossible to determine both the momentum and position of an electron
What are the quantum numbers and what do they describe?
They describe the location of an electron
Principal Quantum Number (first number)
- denoted as n
- larger the value indicates the higher the energy level
and radius
- corresponds to the row or period
Azimuthal Quantum number (second number)
- denoted as ℓ
- describes the shape and number of subshells
- 0: s subshell
- 1: p subshell
- 2: d subshell
- 3: f subshell
- larger the value the greater the energy level
Next is Magnetic Quantum Number (mℓ) then Spin Quantum Number (ms)
What is electron configuration? Aufbau Principle? Hund Principle? Pauli Princple?
Ex: 1s2, 2s2, 2p4 is electron configuration for O
If anion: add another electron so 2p4 becomes 2p5, if cation:
Aufbau: electrons fill from low to high energy levels and fill shells fill completely before filling next energy level
Hund: electrons fill all half shells first then double up (this minimizes repulsion), this makes it so half and fully filled orbitals have lower energy
Pauli: electrons have opposite spins
Paramagnetic vs. diamagnetic?
Paramagnetic: means has unpaired electrons, is attracted to magnets, parallel spin alignment and magnetic field lines bend toward material
Diamagnetic: means all paired electrons, is repelled by magnets, anti-parallel spin alignment and magnetic field lines bend away from material
Periods/groups correspond to rows/columns? Valence electrons?
Periods are rows
Groups are columns (which corresponds to # of VE’s)
What is the periodic notation?
Top is atomic number next is the element and bottom is the atomic weight
Metals vs. nonmetals vs. metalloids characteristics?
Metals: left side of periodic table
- low electronegativity
- low charge
- large atomic radius
- small ionic radius
- LOW IONIZATION ENERGY
- GOOD CONDUCTOR
Nonmetals: right side of periodic table
- HIGH IONIZATION ENERGY
- high electronegativity
- POOR CONDUCTOR
Metalloids: b/w transition metals and right side
- semi-metal so mixed characteristics
How do you determine the smallest ionic radius in an isoelectric series?
Vs. atomic radius
Just know that cation = smallest and anions = biggest b/c isoelectric so only that (+) or (-) matters
Atomic radius is determined by periodic table
What is Zeff and where is it largest of periodic table?
Effective nuclear charge or the pull of valence electrons to the nucleus
It increases from left to right across a period because more valence electrons = more attraction with nucleus
What do the noble gases represent?
The ideal valence electron configuration, most stable/inert/nonreactive
What is the atomic radius periodic table trend?
Atomic radius is highest in the bottom left corner of the periodic table
Left because a lower Zeff holds valence electrons less tightly
Bottom because shells are added resulting in valence electrons being farther away
What is the ionization energy periodic table trend?
Ionization energy is highest in the top right corner of the periodic table
It is the energy required to remove an electron from the nucleus so the closer it is to the nucleus the harder it is to remove
What is the electronegativity periodic table trend?
Electronegativity is highest in the top right corner of the periodic table
It is a measure of the attractive force to an electron, how well it can tolerate a (-) charge
What group are alkali metals/alkaline earth metals/halogens/noble gas located in?
Transition metals?
Alkali metals: Group 1 (reactive)
Alkaline earth metals: Group 2 (reactive)
Halogens: Group 17 (reactive with G1,2 metals)
Noble Gas: Group 18 (inert, high IE, no electronegativity, low BP)
Transition metals: the stuff in the middle (high BP and MP, good conductors)
Ionic bond vs. covalent bond characteristics?
Ionic bonds:
- significantly different electronegativities (metal and
non-metal)
- higher BP and MP than covalent because of
electrostatic attraction
- readily dissolve in water and polar solvents
- aqueous: good conductors
- solid: form a crystalline lattice
Covalent:
- similar electronegativities
What are bond length trends?
C≡C is shortest and strongest
C-C is longest and weakest
Bond length increases w/ atomic radii so larger atomic radii = weaker bond
What are bond energy trends?
Energy required to break a bond so higher bond energy = stronger bond
What is polarity? In bonding?
Refers to the electronegativity difference b/w atoms that creates a dipole with positive end at less electronegative atom
Polar bonds: unequal sharing of electrons from electronegativity difference
Non-Polar bonds: equal sharing of electrons or diatomic (O2, N2, etc.)
What are coordinate bonds? Coordination number? Usually a lewis acid/base?
Bonds where both pairs of bonding electrons come from the same atom, USUALLY COORDINATE COVALENT
Coordination number: number of atoms bound to a central atom
Central atom is usually lewis acid and ligands are usually lewis base
How do you calculate formal charge?
FC = VE - sticks - dots
sticks being number and dots being individual electrons in LP’s
What is resonance?
Molecular structures w/ the same arrangement of atoms but differ in the placement of electrons
Exist as hybrid structures with electron delocalization
The more stable a resonance structure the more it contributes to the hybrid structure
What three things can determine stability of a molecule?
1) lower FC
2) less separation of opposite charges
3) (-) charge on more electronegative atom
VSEPR Shit…
2 electron clouds: linear (180)
3 electron clouds: trigonal planar (120)
w/ a LP: bent
4 electron clouds: tetrahedral
w/ a LP: trigonal pyramidal
5 electron clouds: trigonal bipyramidal
Single/sigma bond vs. double/pi bond?
Sigma bonds have head to head overlap and free rotation
Double bonds are made up of a sigma bond and a pi bond that makes it have side to side or parallel overlap and no free rotation
What are the three types of IMF’s?
1) London Dispersion Forces
- short-lived attractive/repulsive interactions by shifting
dipoles
- everything has these
2) Dipole-Dipole
- when polar molecules orient such that the partial
negative regions are near the partial positive region of
another molecule
3) H-Bonding
- Partial positive H interacts w/ partial negative (F, O, N)
that is nearby
- INCREASES BOILING POINT
IMF’s when summed together can be quite impressive
How many particles are in a mole?
6.022x10^23
What are equivalents?
The number of mols of the interested substance does one mole of a given compound produce
= mass of compound (in grams) / gram equivalent weight
What is gram equivalent weight?
the amount of compound, in grams, that produces one equivalent of a particle
= molar mass/n n: # of particles produced/consumed
What is normality?
A measure of concentration using equivalents (equivalents / L)
Molarity = normality/n
