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• Bohr’s Model• Further away from the nucleus means more energy.• There is no “in between” energy levels• The Quantum Mechanical Model• The atom is found inside a blurry “electron cloud - area where there is a chance of finding an electron.• 90 % is called - Atomic Orbital• Principal Quantum Number (n) = the energy level of the electron.Within each energy level the complex math of Schrodinger’s equation describes several shapes.• These are called atomic orbitals Regions where there is a high probability of finding an electron.• S orbitals • 1 s orbital in every energy levelSpherical shaped Each s orbital can hold ONLY 2 electronsCalled the 1s, 2s, 3s, etc.. orbitals.• P orbitalsStart at the second energy level -2P • 3 different directions - X,Y,Z axis Each can hold 2 electrons• D orbitalsStart at the third energy level , 5 different shapes (directions),Each can hold 2 electrons• F orbitals Start at the fourth energy level,Have seven different shapes. 2 electrons per shape• First Energy Level• only s orbitalonly 2 electrons - 1s2• Second Energy Levels and p orbitals are available2 in s, 6 in p (3 p orbitals in each n)2s22p6 =8 total electrons can fit• Third energy levels, p, and d orbitals2 in s, 6 in p, and 10 in d (5 d’s)3s23p63d1018 total electrons• Fourth energy levels,p,d, and f orbitals 2 in s, 6 in p, 10 in d, ahd 14 in f4s24p64d104f1432 total electrons• Any more than the fourth and not all the orbitals will fill up in order expected,The energy levels overlap• Lowest energy orbitals fill first.• Aufbau principle- electrons enter the lowest energy first.(This causes difficulties because of the overlap of orbitals of different energies)• Pauli Exclusion Principle- at most 2 electrons per orbital – Must have different spins• Hund’s Rule- When electrons occupy orbitals of equal energy they don’t pair up until they have to .• The Diagonal RuleFill from the bottom up following the arrows• If we write these electron configurations:Titanium - 22 electrons -1s22s22p63s23p64s23d2Vanadium - 23 electrons 1s22s22p63s23p64s23d3Chromium - 24 electrons1s22s22p63s23p64s23d4 is expected But this is wrong!!• Chromium is actually1s22s22p63s23p64s13d5• LightThe study of light led to the development of the quantum mechanical model.Light is a kind of electromagnetic radiation.• Electromagnetic radiation includes many kinds of waves All move at 3.00 x 108 m/s ( c)• Parts of WaveOrgin - the base line of the energy.Crest - high point on a waveTrough - Low point on a waveAmplitude - distance from origin to crestWavelength - distance from crest to crest• Wavelength - is abbreviated l Greek letter lambda. - ג• Frequency - vThe number of waves that pass a given point per second.Units are cycles/sec or hertz (hz)Abbreviated n the Greek letter nu - v• c is the speed of light c = ג v• Frequency and wavelengthAre inversely relatedAs one goes up the other goes down.Different frequencies of light is different colors of light.There is a wide variety of frequenciesThe whole range is called a spectrum• Atomic SpectrumEach element gives off its own characteristic colors.• Light is a Particle + Wave • Energy is quantized.Light is energy• These smallest pieces of light are called photons.• Energy and frequency are directly related. • When we write electron configurations we are writing the lowest energy.The energy level and electron starts from is called its ground state.• Heat or electricity or light can move the electron up energy levelsAs the electron falls back to ground state it gives the energy back as light Further they fall, more energy, higher frequency.• the orbitals also have different energies inside energy levelsAll the electrons can move around.• What is light - Dual Nature of Light • Light is a particle - it comes in chunks.• Light is a wave- we can measure its wave length and it behaves as a wave• If we combine E=mc2 , c= ג, E = 1/2 mv2 and E = h v We can get ג = h/mv (De Broglie’s eq.)The wavelength of a particle!!!• Matter is a WaveDoes not apply to large objects (Things bigger that an atom) A baseball has a wavelength of about 10-32 m when moving 30 m/s An electron at the same speed has a wavelength of 10-3 cm - big enough to measure. • Heisenberg Uncertainty PrincipleIt is impossible to know exactly the speed and velocity of a particle.The better we know one, the less we know the other.The act of measuring changes the properties.• More obvious with the very small matter To measure where a electron is, we use light.But the light moves the electron• And hitting the electron changes the frequency of the light.
