Modern Atomic Theory Review

• ^^light is a form of electromagnetic radiation^^
    * properties of both waves and particles:
      * wavelength (λ) - the distance between adjacent wave crests, meters
        * red light (750 NM) has longest wave length
        * violet light (400 NM) has shortest wave length
        * ==1 NM = 1 * 10^-9 meters==
      * frequency (v) - number of cycles or crests that pass through a stationary point in one second
      * amplitude - the height of the wave from zero to crest
    * ^^wavelength and frequency are inversely/indirectly related^^ - the shorter the wavelength, the higher the frequency

   
  * ==speed of light====: 2.998 * 10^8 meters/second = λv==

• electromagnetic radiation
    * light can be viewed as a stream of particles
      * particle of light is a ^^photon^^
      * photon - a single packet of light energy
        * has specific wavelength, determines what light we see
        * wavelengths of spectral lines are characteristics of the element
          * make up atomic emission spectra
        * no two elements have the same emission spectra
      * amount of energy carried in the packet depends on the wavelength of the light - ^^the shorter the wavelength, the greater the energy^^
        * light waves that carry more energy in their crests are closer
        * violet light carries more energy per photon than red light
    * the photoelectric effect - the emission of electrons from a metal when light shines on the metal
      * ^^quantum of energy^^ - the minimum quantum of energy that can be lost or gained by an atom
      * ^^quantized^^: an electron has to absorb/emit a specific amount of energy to move from one energy level to another
        * ^^ground state^^: the normal energy level any given electron occupies
        * ^^excited state^^: the energy level an electron occupies when it has absorbed the specific quantum of energy to move up to that level
      * %%Planck’s Law%% - ==E=Hv==
        * E - energy, joules
        * H - ==Planck’s constant, 6.626 * 10^-34 J*S==
        * v - frequency
• %%Bohr’s Model%%
    * Niels Bohr changed Rutherford’s model to include newer discoveries about how the energy of an atom changes when the atom absorbs/emits energy
      * proposed electron is found only in specific circular paths/orbits around the nucleus ❌
        * incorrect - if the orbits were truly circular, the electron would spiral into the nucleus
      * each possible electron orbit has a fixed energy - ^^energy level^^ ✅
      * each orbit is a specific distance from the nucleus and at each specific energy
        * ^^impossible for an electron to exist between orbits^^
      * ^^amount of energy is directly related to the frequency → wavelength^^
• %%de Broglie%%: proposed “electrons be considered as waves confined to the space around an atomic nucleus”
• %%Heisenberg Uncertainty Principle%%
    * Werner Heisenberg
    * states that it is impossible to determine simultaneously both the position and velocity of an electron
    * “we cannot know both the position and speed of a particle, such as a photon or electron, with perfect accuracy”
      * %%Schrödinger Wave Equation%%
        * Erwin Schrödinger developed an equation that treated electrons as waves
        * ^^Quantum Theory^^ - describes mathematically the wave properties of electrons
          * electrons exist in certain regions called orbitals
          * orbitals - 3D regions around the nucleus that indicate the probable location of an electron
            * represent probability maps showing a statistical attribution of where the electron is likely to be found
        * 4 Wave Properties
          * ^^Energy Level^^: Principal Quantum Numbers - number specifying the principle shell of orbital
            * n - indicates the energy level
            * energy increases with principal quantum number
            * maximum of 7 energy levels
            * ==n^2== - how many orbitals in any energy level
            * ==2n^2== - maxim. number of electrons possible in any energy level
          * ^^Sub Level^^: Shapes of Quantum Mechanical Orbitals
            * letter indicates subshell of orbital, specifies shape
            * possible letters - s, p, d, f
            * electrons are more likely to be found closer to the nucleus than farther away
          * ^^Orbital^^: Orientation
            * s - 1 orbital
            * p - 3 orbitals
            * d - 5 orbitals
            * f - 7 orbitals
          * ^^Spin^^: clockwise or counterclockwise

• Electron Configuration
    * arrangement of electrons in an atom and the way in which the electrons are arranged in various orbitals around the nucleus
    * %%Aufbau Principle%%
      * the electrons will fill the orbitals in a very specific order
      * lowest → highest energy
      * ^^The Diagonal Rule^^

   
  * %%Pauli Exclusion Principle%%
    * an individual orbital may describe at most TWO electrons
    * in order to occupy the orbital, the two electrons must have opposite spins: ⬆⬇
  * EXAMPLES
    * Carbon 6e- : 1s^2, 2s^2, 2p^2
    * Aluminum 13e- : 1s^2, 2s^2, 2p^6, 3s^2, 3p^1
  * Noble Gas Configuration
    * Aluminum 13e- : [Ne] 3s^2, 3p^1

• %%Hund’s Rule%%
    * orbitals in the same sub-level must all fill with one electron before a second electron is added to any of the orbitals: (n)p^4 - ⬆⬇ ⬆ ⬆
    * the “single” electrons will all have the same spin direction
    * Orbital Diagram

• @@Valence@@ and $Core$ Electrons
    * valence electrons are the electrons on the outermost energy level
    * the noble gases always have full valence shells
    * Selenium 34e- : $1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 3d^10,$ @@4s^2@@, $3d^10,$ @@4p^4@@
    * Silicon 14e- : $1s^2, 2s^2, 2p^6,$ @@3s^2, 3p^2@@
    * the chemical properties of elements are largely determined by the number of valence electrons they contain
    * properties vary in a periodic fashion because the number of valence electrons is periodic
• Atomic Physical Properties
    * Atomic Size ⬇⬅
      * left-right ^^decreases ⬅^^
        * across a period, the amount of protons in the nucleus increases which has a stronger pull on the electrons, causing them to move closer to the nucleus
      * top-bottom ^^increases ⬇^^
        * size of the orbital increases with increasing principal quantum shell number
        * electrons occupying the outermost orbitals are farthest from nucleus
    * Ionization Energy ⬆➡
      * amount of energy needed to remove a single electron
      * left-right ^^increases ➡^^
        * electrical pull on electrons from the # protons in nucleus causes increases amount of energy needed
      * top-bottom ^^decreases ⬆^^
        * electrons in outermost orbitals are less affected by the electrical pull from nucleus
    * Electronegativity ⬆➡
      * ability of an atom of an element to attract electrons when the atom is in a compound
      * left-right ^^increases ➡^^
      * top-bottom ^^decreases ⬆^^