Atoms, Molecules, and Quantum Mechanics Flashcards
atoms
nucleus surrounded by 1+ electrons
nucleus contains
protons and neutrons
charge and mass of atomic particles
proton: 1+ charge, ~ 1 amu
neutron: neutral charge, ~ 1 amu
electron: 1- charge, 5.5 x 10^-4 amu
elements
building blocks of compounds, can’t be broken down further
atomic notation
^A _Z X
A = mass number (protons + neutrons)
Z = atomic number, number of protons, defines the element
isotopes
same element with different number of neutrons, named by mass number
atomic weight/molar mass (MM or M)
in atomic mass units (amu) or u
one atom of 12C has atomic weight of 12 amu
mass from periodic table…
amu or g/mol
mole
6.022 x 10^23 of something = Avogadro’s #
moles = grams/molecular weight
6.022 X 10^23 amu =
1 gram
periodic table rows and columns
horizontal row = period
vertical column = group/family
metals ___ electrons
lose electrons –> positive ions or oxidation states
metal characteristics
lustrous, ductile (easily stretched), malleable (hammered into think strips), thermally and electrically conductive
all exist as solids at room temp except mercury
1st and 2nd group metals
1st group = alkali metals (most reactive)
2nd group = alkaline earth metals
nonmetals form…
negative ions (gain electrons) generally lower melting points
last 2 groups of nonmetals
2nd to last = halogens
last group = noble gases (inert gases)
transition metal position in periodic table
the 10 shorter groups in middle
elements in the same family/group…
make same number of bonds, exist as similarly charged ions (except hydrogen)
cations
+ , metals
anions
- , nonmetals
transition metals loss of e’s from…
s first, then d
electron shielding
first electrons shield some of nuclear charge from others –> Zeff
Zeff
effective nuclear charge, amount of charge felpt by electron after shielding
atomic radius periodic trend
increase from L bottom
atoms get smaller when add electrons
bigger as add new shell / move down a period
Zeff periodic trend
increases L –> R
each new electron closer and held more tightly to nucleus
ionization energy periodic trend
increases L –> R and bottom –> top
ionization energy
energy needed to detach e- from nucleus
second ionization energy - energy to remove 2nd e –> 2+ cation, always much greater than the first
electronegativity
tendency of an atom to attract the shared e’s
large electronegativity difference = ionic bonds
moderate difference = polar covalent
minor difference = nonpolar covalent
electronegativity periodic trend
increases L –> R and bottom –> top
undefined for noble gases (don’t make bonds)
electron affinity
willingness of atom to accept additional e, energy released when e is added
electron affinity periodic trend
increase L–R and bottom –> top
get more exothermic
noble gases of endothermic (don’t follow trend)
metallic character periodic trend
increase L bottom
SI units: mass, length, time
kg, m, s
SI units: electric current, temp, luminous intensity
electric current: ampere, A
temp: K
luminous intensity: candela, cd
newton units
kg*m/s^2
prefixes: mega, kilo
mega = M 10^6 kilo = k 10^3
prefixes: deci, centi, milli
deci = d 10^-1 centi = c 10^-2 milli = , 10^-3
prefixes: micro, nano, pico, femto
micro = mu 10^-6 nano = n 10^-9 pico = p 10^-12 femto = f 10^-15
covalent bond
2 electrons shared by 2 nuclei
bond length
point where the energy level is the lowest
2 atoms will only form bond if they can lower their overall energy level by doing so, nature seeks lowest energy state
energy needed to ___ bond
break bonds (no energy released from breaking bond)
bond dissociation energy / bond energy
energy to achieve complete separation
between energy at bond length and zero
empirical formula
whole # ratio of relative number of atoms
ex: CH2O
molecular formula
exact # of elements
ex: C6H12O6
percent composition by mass
ex: of carbon in glucose
(mol. weight of carbon * ratio)/mol. weight of glucose
empirical formula from mass composition
assume 100 g sample
ex: 6% H 94% O
6g/ 1g/mol = 6 moles
94g/16g/mol = 5.9 moles
naming copper(I) and (II)
(I) = cuprous (II) = cupric
naming NO2- vs NO3-
hypo-ite
NO2- = nitrite
NO3- = nitrate
per-ate
“runs to completion”
move to right until supply of at least 1 reactant is depleted
most reach equilibrium first and don’t run to completion
find limiting reagent
use mole ratios to find how much of other reactant would be needed if other is used up
one will be not enough –> limiting reagent
theoretical yield
amount of product when reaction runs to completion (calculated)
percent yield
actual/theoretical x 100
combination reaction
A +B –> C
decomposition reaction
C –> A + B
single displacement reaction
A + BC –> B + AC
double displacement reaction
AB + CD –> AD + CB
“delta” triangle above/below reaction arrow
heat is added
“naught” circle symbol
standard state conditions
quantum mechanics
elementary particles can only gain/lose energy and other quantities in discrete units
quantum numbers
set of 4 numbers, the ID # of the electron
Pauli exclusion principle
no 2 e’s in the same atom can have the same 4 quantum #s
principle quantum number
n, shell level for electron, energy level
azimuthal quantum number
l, subshell shape l = 0 s = 1 p = 2 d = 3 f
magnetic quantum number
ml, precise orbital of given subshell
from -l –> +l
electron spin quantum number
ms, distinguish the 2 e’s that may occupy same orbital +1/2 or -1/2
number of total orbital in a shell
n^2
1,4,9,16… with 2 e’s in each orbital
Heisenberg Uncertainty Principle
uncertainty in the product of position of particle and its momentum, on order of Plank’s constant
-more known about position, less about momentum
Aufbau principle
each new e- added to lowest energy level available
shell level of most recently added e- corresponds to…
period number
- transition metals: one behind the period
- lanthanides and actinides (2 period under table): 2 behind period
subshell
orbital shape, 90% chance of finding the e- in shape
s subshell shapes
circles, 1s smallest, get bigger as numbers increase
p subshell shape
flower petal around axis
ex: 2px, 2py, 2pz
valance electrons
outermost shell, contribute most to chemical properties
electron configuration
list shells and subshells w/ superscript to show # of e-s
Na: 1s2, 2s2, 2p6, 3s1
Br: 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p5
abbreviated electron configuration
use next smallest noble gas
ex: [Ar] 4s2 3d10 4p5
ground state
e- all in lowest energy level
configurations for ions/atoms w/ excited e-s
+ charge, take away 1
- charge, add 1
total number of e- in configuration = total # in atom
Hund’s rule
e’s wont fill any orbital in same subshell until all orbital s in that subshell contain at least 1 electron, unpaired e’s will have parallel spins
Plank’s Quantum Theory
delta E = hf
if transfer energy via electromagnetic wave, increase energy w/out changing frequency, can only change in discrete increments, radiation must be emitted or received in energy packets
photoelectric effect
kinetic energy of e’s increases only when frequency is increased
- photon released when e- falls to lower energy shell
- electron bumped up to excited state after absorbing a photon
- electrons ejected by one-to-one photon-electron collisions
