1 Atomic Structure Flashcards
valence electrons
outermost shell of electrons –> higher energy
have strongest interactions with surroundings
isotopes
varying mass numbers
atomic weight
weighted average of different, naturally occurring, isotopes
Avogadro’s number
1 mole = number of whatever “things” one is concerned about
= 6.02 x 10^23
Planck relation
energy omitted as electromagnetic radiation from matter
comes in discrete bundles called quanta
Planck’s equation
E = hf
h = Planck’s constant = 6.626 x 10^(-34) J s
Bohr’s model
angular momentum of electrons orbiting hydrogen nucleus
Bohr’s equation
L = n h / 2 pi
energy of electron orbiting hydrogen nucleus
E = -R(H) / n^2
ground state
state of lowest energy of atom
(all electrons in lowest possible orbitals)
all systems tend towards minimal energy)
excited state
at least 1 electron moves to subshell of higher than normal energy
atomic emission spectra
fingerprints of electron transition
identifies element by line spectra
application of Bohr’s model
equation for energy of emitted photon
E = hc / lambda = -R(H) [(1/n(i)^2) - (1/n(f)^2)]
atomic absorption spectra
at specific wavelengths
accurate to make electro transition to “excited”
also a fingerprint (element-specific)
required when element is in gas phase
application of Bohr’s model
orbitals
electrons move rapidly around nucleus – localized to regions
Heisenberg Uncertainty Principle
impossible to determine simultaneously, accurately, both momentum AND position of electron
IF want position, electron must stop (no momentum)
IF want momentum, electron must move (lose position)
Pauli Exclusion Principle
no two electrons in a given atom can possess the same 4 quantum numbers
principle quantum number (n)
shell
increasing n increases energy level and radius of shell
max number of electrons within shell
2n^2
azimuthal (angular momentum) quantum number (l)
shape and number of subshells
any value 0 to (n-1)
max number of electrons within subshell
4l + 2
magnetic quantum number (m(l))
specifies orbital
any value -l to l
spin quantum number (m(s))
+(1/2) or -(1/2)
paired spins –> same orbital
parallel spins –> different orbitals
Aufbau Principle
building-up principle
each subshell fills completely before electrons begin filling next one
Hund’s rule
orbitals filled first with maximum number of parallel spins before paired spins
(electron repulsion)
paramagnetic material
atoms with unpaired electrons, will orient spins in alignment with magnetic field
attraction
diamagnetic material
atoms with only paired electrons
slightly repelled by magnetic field
