𝑭𝒐𝒓𝒄𝒆=𝒌 𝒒 𝟏 𝒒 𝟐 𝒓 𝟐 Bohr Model (Shell Model) Evidence suggested electrons occupied specific energy levels (shells) while “orbiting” around nucleus Essentially based on Coulomb’s Law k = coulomb’s constant q = object with a charge r = radius (distance between the 2 charged particles) 𝑭𝒐𝒓𝒄𝒆=𝒌 𝒒 𝟏 𝒒 𝟐 𝒓 𝟐 Was used to help explain why electrons didn’t come “crashing” into the nucleus (since opposites attract) Attractive force between nucleus and electron is balanced by electron’s centrifugal force The Bohr model makes great predictions BUT there’s a couple things about electrons we discovered: Uncertainty Electron spin

Orbital Electrons have a Spin Uncertainty: We can never know BOTH the: - Heisenberg Uncertainty Principle We can never know BOTH the: Location of an electron Momentum of an electron Because of this, we realized that electrons live in these “clouds” of probability Don’t follow specific orbits Orbital Where electrons spend their time Electrons have a Spin Clockwise or counter-clockwise magnetic spin As a result of this electron spin: Only two (max) electrons can exist in an orbital This forced us to modify our “shell” (Bohr) model in order to better align with the evidence of reality Quantum mechanical model of the atom Computers allowed us to complete complex equations and software to predict how atoms are going to interact

Orbitals s orbital d orbitals p orbitals f orbitals ALL of these orbitals simply represent “clouds” of probability where electrons sit p orbitals f orbitals

Quantum Numbers Size (n) Shape (l) Orientation (ml) Spin (ms) Size of the orbital As n gets larger then the area in which the electron occupies gets larger as well These numbers allow us to predict WHERE electrons are most likely to be found which allows us to predict: What an atom looks like How atoms are going to interact Shape (l) Shape of the orbital Can be either an s, p, d, f Orientation (ml) Tells us the number of orientations the orbitals can have s 1 orientation p 3 orientations d 5 orientations f 7 orientations Spin (ms) Clockwise (+1/2) Counter-clockwise (-1/2) Dictates that only 2 electrons can exist in an orbital

Electron Configuration Distribution of electrons Where the electrons are found in atoms OR in ions Ionization energy Amount of energy it takes to remove an electron Can be quantified using Coulomb’s Law Multielectron atoms or ions Shells, subshells, and orbitals similar ionization energy Nucleus Core electrons Valence electrons shield

hydrogen Atomic number Each box represents and orbital Each arrow represents an electron

helium Atomic number Each box represents and orbital Each arrow represents an electron

lithium Atomic number Each box represents and orbital Each arrow represents an electron

beryllium Atomic number Each box represents and orbital Each arrow represents an electron

boron Atomic number Each box represents and orbital Each arrow represents an electron

carbon Atomic number Each box represents and orbital Each arrow represents an electron

nitrogen Atomic number Each box represents and orbital Each arrow represents an electron

oxygen Atomic number Each box represents and orbital Each arrow represents an electron

fluorine Atomic number Each box represents and orbital Each arrow represents an electron

neon Atomic number Each box represents and orbital Each arrow represents an electron

sodium Atomic number Each box represents and orbital Each arrow represents an electron

magnesium Atomic number Each box represents and orbital Each arrow represents an electron

Periodicity 1s1 hydrogen 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f

Periodicity 1s22s22p1 boron 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f

Periodicity 1s22s22p6 neon 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f

Periodicity 1s22s22p63s1 sodium 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f

Periodicity 1s22s22p63s23p64s23d4 chromium [Ar]4s23d4 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s 7p chromium 1s22s22p63s23p64s23d4 Same thing [Ar]4s23d4