Exam 1 Flashcards
Lectures 1-16
isotopes
atoms of an element with the same number of protons but different number of neutrons
isotopes of same element have similar chemical properities, form same compounds, and display similar reactivities
atomic mass
- mass of an atom in atomic mass units (amu)
- on periodic table, it is the average mass of the naturally occuring mixture of isotopes
number on periodic table below the element symbol
average atomic mass
weighted average of all the naturally occuring isotopes of the element
atomic number
protons
number on periodic table above the element symbol
mass number
not on periodic table
protons + neutrons
quantization of energy
stairs analogy
* electron can be on any step but not in between
* higher the energy, higher level = excited state
quantum model of atom
there is no particular distance at which the electron is located from the nucleus b/c they have wave and particle characteristics
- electrons don’t occupe just a single point in space
- wave behavior of electron is wave function
electron density
probability of finding an electron in a certain area of space
- results in electron moving rapidly in the orbital b/c faster = more likley to be in certain regions
- proportional to wave function squared
orbital
locations in space around nucleus at which the probably of finding the electron has higher values
Heisenberg Uncertainty Principle
it is impossible to know simultaneously the momentum (p) and position of a particle (x)
momentum refers to the particle’s motion/how fast it’s going
p=mv
principle quantum number (n)
which shell has the most energy
describles electron shell and specifies size of the shell
outer shell = most energy b/c it’s the furthest from the nucleus so more freedom to move
angular moment quantum number (l)
specifies shape of orbital
l ≤ n-1
- s can hold up to 2 e- and has 1 orbital
- p can hold up to 6 e- and has 3 orbitals
- d can hold up to 10 e- and has 5 orbitals
- f can hold up to 14 e- and has 7 orbitals
- l=0 → s
- l=1 → p
- l=2 → d
- l=3 → f
magnetic quantum number (ml)
specifies position of orbital
-l ≤ ml ≤ l
ex. for the p-orbital, there is
* ml = -1 for the px orbital
* ml = 0 for the py orbital
* ml = +1 for the pz orbital
electron spin (ms)
ms = +1/2, -1/2
Pauli Exclusion Principle
seats in a football stadium analogy
no 2 electrons in an atom can have the same 4 quantum numbers (n, l, ml, ms)
number of electrons in a shell formula
2(n)^2
energy level for orbital diagrams
lower = closer to nucleus = lower energy (b/c electrons are closer to protons which means more stable) more stable = less energy
shielding
inner electrons block outer electrons from protons
- electrons in the same energy level shield each other
Aufbau Process
- electrons occupy the lowest energy possible
- Hund’s Rule: every orbital is singly occupied w/ one electron before any are doubly occupied
- Pauli exclusion principle: no 2 electrons in an atom have the same 4 quantum numbers
Aufbau process exceptions
transition metals
lanthanides
actinides
how do you know which could represent the electron in the highest energy shell
the coefficient
inner core electrons
those an atom has in common w/ the previous noble gas
outer electrons
those in the highest energy level (highest n-value)
valence electrons
involved in bonding
- main group: valence electrons are the outer electrons
- transitional metals: valence electrons are outer electrons and (n-1)d electrons (only if d is not fully filled)