Chapter 5

 Energy transmitted from one place to another by light in the form of waves  3 properties of a wave;  Wavelength  Frequency  Speed

 Wavelength – length of a wave [measured in nm]; represented by the Greek letter lambda ( λ )  The distance between peaks.

 Amplitude – The vertical distance from the middle of the wave (undisturbed position) to the crest or trough.  Peak/Crest – top of a wave  Trough – bottom of a wave

 Frequency – number of waves that pass through a given point in a specific amount of time. [waves/sec or hertz(Hz)]; represented by the Greek letter nu ( ν )  Speed of electromagnetic radiation (c) = 3.0 X 10 8 m/sec

 Speed of Light (c) = wavelength x frequency [Inversely proportional]  3.0 x 10 8 m/s = λ x ν  All radiation moves at the same speed!

 Light’s particle like qualities seen and explained through:  Photoelectric effect – light shining on a metal emits electrons  Light is a stream of tiny packets of energy called photons.

 Planck’s Equation:  Energy = Planck’s Constant (h) x Frequency (v) E (photon) = h x v  E = energy of quantum radiation, in Joules (J)  h = Planck’s constant x J * s  v = frequency of radiation emitted (Hertz or 1/sec)  Frequency and Energy are directly proportional.

 Continuous Spectrum (visible spectrum) – rainbow of colors within a given range [roygbiv]  Bright line Spectrum – consists of several distinct lines of color each with its own frequency [also called Line emission spectrum]; each element has characteristic line emission spectrum.  Hydrogen’s Line Emission Spectrum: Series of specific wavelengths of emitted light – Lyman series (ultraviolet), Balmer series (visible), Paschen series (infrared); we can only see Balmer.

 Bohr’s model: stated that hydrogen atoms are quantized and exists in certain definite energy levels.  Electrons circle nucleus in orbits  Energy level low closest to nucleus  Quantum = finite quantity of energy that can be gained or lost by an atom  Photon = packet of light (quantum); particles of radiation  Radiation emitted and absorbed in whole number of photons; minimum energy needed to eject an electron

 Energy states of an atom: Ground state – lowest energy state of an atom and electrons Excited state – atom has higher potential energy than a ground state. (electrons are excited)  When an atom returns to ground state it releases or gives off energy it gained in the form of electromagnetic radiation.

 Quantum Theory: describes mathematically the wave properties of electrons and other very small particles.  Quantum numbers: properties of orbitals and electrons in the orbitals.  Orbital is a 3 dimensional place around the nucleus that indicates the probable location of an electron. 

 There are Four Quantum Numbers that are designated for each electron on an atom.  Principle quantum number: (n) main energy level occupied by an electron increases so does electron’s energy and distance (1 through 7)  Angular Momentum Quantum Number: sublevels (l) indicate the shape of the orbital  Letter (orbital shapes)Shape  s sphere  p dumbbell  d dumbbell and donut  f Varies

 Magnetic Quantum Number: orientation of an orbital around a nucleus.  s sublevel – one orientation  p sublevel – three orientations  d sublevel has 5 orientations  f sublevel has 7 orientations  Spin Quantum Number: two values: clockwise or counter clockwise

 Electron Configuration: arrangement of electrons in an atom  Heisenberg Uncertainty Principle: it is impossible to determine simultaneously both the position and velocity of an electron or any other particle.  Aufbau principle: an electron occupies the lowest energy orbital that can receive it.  Pauli exclusion principle: no two electrons in the same atom can have the same set of four quantum numbers.

Hund’s rule: orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron and all electrons in singly occupied orbitals must have the same spin. Highest occupied level: electron containing main energy level with highest principle quantum number. Inner shell electrons: not in highest energy level.