Atomic Structure Flashcards
Protons have a mass of…
1 amu (atomic mass unit)
Z stands for
atomic number, the number of protons in an atom of an element
While all atoms of an element have the same atomic number, they do not necessarily have the same…
atomic mass due to isotopes!
A stands for
mass number, the sum of all protons and neutrons within an atom
Isotopes
atoms that have the same atomic number, but different mass numbers
Because subatomic masses are so small, electrostatic force of attraction between protons and electron is….
far greater than the gravitational force of attraction based on mass
Electrons close to the nucleus have..
lower energy levels and strongest interaction with nucleus
Electrons further away from the nucleus…
have higher energy levels and strongest interaction with the surrounding environment
Valence Electrons
electrons in the outer most shell of an atom, they determine the reactivity of an atom
Increase stability
having a full valence electron shell
Cation vs Anion
positively charged atom vs negatively charged atom
Atomic Mass/Mass Number
are synonymous! It varies from one isotope to another
Atomic Weight
Is constant for a given element; the weighted average of all isotope weights
Isotopes
when an element differs in the number of neutrons
but because protons and electrons are constant, they exhibit similar chemical principles
Half life corresponds with and helpd determine…
stability and helps determine proportions of isotopes
Avogadros Number
- 02*10^23 atoms/molecules /ions/things in 1 mole
ex: 12 amu atomic weight of carbon means - 02*10^23 atoms of carbon = 12 amu
Calculating Atomic Weight of an Unknown Element
(% Isotope 1)(atomic mass Isotope 1) + ….. = Atomic Weight
Ernest Rutherford
gave evidence that an atom has a dense, positively charged nucleus that is a small portion of atoms volume
Max Planck
developed first quantum thoery, energy emitted as electromagnetic radiation from matter comes from quanta
Planck Relation
E = hF
E = energy
h = plancks constant
f = frequency of radiation
Bohr Model Postulate
that centripetal force causing electrons to be in orbit is caused due to the electrostatic force between the positively charged protons and negatively charged electrons
Angular Momentums of an Electron Equation
L = nh/2pi
n = quantum number h = plancks constant
angular momentum only changes with respect to the quantum number
Energy of an Electron
E = - Rh / n^2
Rh = rydberg unit of energy
Energy changes with respect to the quantum number like angular momentum
a value of 0 energy states that a proton and electron are…
not attracted at all, not close
Energy of an electron increases…
the farther from the nucleus it is (as quantum number increases)… think energy of an electron equation
Ground State
lowest electron energy
Excited State
highest electron energy as electron moves above to another shell further out
How can electrons be excited?
via heat/energy forms
Emission of photons
when excited form electrons drop back down to ground state, they emit energy in the form of photons
the photon emitted has a wavelength associated with it depending on the specific energy transmission
Electromagnetic Energy of Photons
E = hc/ lambda
lamba = wavelength
h = Planck’s constant
Atomic Emission Spectrum
each element can have its electrons excited to a different set of distinct energy levels giving them a unique atomic emission spectrum
Lyman Series
group of hydrogen emission lines corresponding energy levels n greater than or equal to 2 to n = 1
Balmer Series
group of hydrogen emission lines corresponding energy levels n greater than or equal to 3 to n = 2
Paschen Series
group of hydrogen emission lines corresponding energy levels n greater than or equal to 4 to n = 3
Lyman Series has larger energy transitions than Balmer series therefore it…
has shorter photon wavelengths
Combining Planck’s and Bohr’s Theories states
The energy emitted photon corresponds to the difference in energy between the higher energy initial state and the lower energy final state
Absorption spectrum
in addition to each element having a unique emission spectrum, they also each have a unique absorption spectrum
Emission and Absorption Spectrum
uniques for each element, wavelength for each corresponds with one another because difference in energy levels is unchanged
Quantum Mechanical Model
electrons move rapidly and are localized in regions of space around nucelus known as orbitals
Heisenberg Uncertainty Principle
its impossible to determine perfectly the momentum and position of an electron
Pauli Exclusion Principle
no two electrons in a given atom can possess the same set of 4 quantum numbers
Principle quantum Number (n)
the larger the integer value of n (electron shell), the higher the energy level and radius of the electons shell
Maximum number of Electrons Within a Shell
2n^2
The difference in energy between two shells DECREASES as the distance from the nuclues ___
INCREASES
n=3 to n=4 is lower than n= 2 to n=3
Azimuthal (Angular Momentum) Quantum Number (l)
refers to the shape and number of subshells within a principle energy level
l = all numbers less than n -1
ex: n=2 ; l = 1 or 0
this means there are 2 subshells (1 and 0) within the second principal energy level
l = 0 l = 1 l = 2 l = 3
s, p, d, f orbitals respectively
Maximum Number of Electrons within a subshell =
4l + 2
Magnetic Quantum Number (ml)
specifies the particular orbital within a subshell where an electron is most likely to be found at a given time
- l , 0 , l
s subshell orbital shape
p subshell orbital shape
s subshell have spherical orbitals
p subshell has 3 dumbell type orbitals
As atomic number increases, so too does the number of….
electrons
Spin Quantum Number (ms)
spin orientation +1/2 or -1/2
Parallel Spins
Electrons in different orbitals with the same ms values
Example: 2p^4
Indicates that 4 electrons in the second p subshell of second principal energy level is filled, also that all energy levels below 2p are filled
Aufbau Principle
each subshell will fill completely before electrons enter the next one
n + l rule
ranks subshells by increasing energy
the lower the sum of n+l,, the lower the energy of the subshell.
IF n+l are equal, then the subshell with the lower n has the lower energy and will fill first **pg 21
***Subshells for cations
start with neutral element and then remove electrons from subshells with the highest n value
Ex: electron configuration of Fe 3+
Neutral: [Ar] 4s^2 3d^6
Cation: [Ar]3d^5
Hunds RUle
within a given subshell, orbitals are filled so maximum number of half-filled orbitals with parallel spins (each orbital has an electron before one is completely filled)
Notable exceptions to Electron Config
Chromium and ELements in its group [Ar]4s13d4
Copper and elements in its group [Ar]4s13d10
The presense of paired or unpaired electrons affects the….
chemical and magnetic properties of an atom or molecule
Paramagnetic
unpaired electrons will orient their spins in alignment with a magnetic field and material will be attracted to the field
Diamagnetic
materials with paired electrons will be slightly repelled y a magnetic field
Valence ELectrons for Groups 13-18
highest s and p subshell electrons are the valence electrons
Valence Electrons for Transition Elements
highest s and d subshell electrons
All elements in period three (startng with sodium) and below may accept electrons into….
their d subshell and hold more than 8 electrons in the valence shell
