Presentation on theme: "CHAPTER 5: ELECTRONS IN ATOMS"— Presentation transcript:
1 CHAPTER 5: ELECTRONS IN ATOMS Rutherford’s model of the atom did not explain how the electrons occupy the space surrounding the nucleus.Recall:Opposites attract….right??In the early 1900’s, investigations using the relationships that exist between light and electrons will reveal a more accurate model of the atom.Model ofThe Atom
2 Emission Spectrumatoms can exist in low energy states called ground states or at high energy states called excited states.when excited atoms return to ground states, it gives off energy in the form of electromagnetic radiation.all elements have a characteristic emission spectra that corresponds to the amount of energy given off.Ground &ExcitedStatesEmissionSpectra
3 Probability of Finding an Electron in a Hydrogen Atom.
4 The Bohr Model ---it’s really not boring Niels Bohr linked photon emission with an atom’s electrons.electrons exist in fixed orbits and never in between.his model only explains the emission of Hydrogen atoms.NielsBohrFlame TestEmissionFlame TestExplanationThe Quantum Model of the AtomLouis deBroglie suggested that electrons be considered waves confined to the space around the nucleus.
5 electrons, like waves, are capable of interference. investigations also confirmed that electrons can be bent or diffracted.electrons, like waves, are capable of interference.Wave PropertiesOf ElectronsHeisenberg Uncertainty Principle: it is impossible to determine simultaneously both the position and velocity of an electron.HeisenbergErwin Schrodinger’s wave equation and Heisenberg’s Uncertainty Principle laid the foundation for the quantum model of the atom.electrons do not travel in specified orbits.instead electrons exist in regions called orbitals.Quantum Modelof the Atom
6 Electron Configurations “The arrangement of electrons in an atom”Rules Governing Electron ConfigurationsAufbau Principle: an electron occupies the lowest-energy orbital that can receive it.2. Pauli Exclusion Principle: no two electrons in the same atom can have the same set of four quantum numbers.QuantumSubshells
7 3. Hund’s Rule: orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron.all electrons in singly occupied orbitals must have the same spin.Orbital Notationa way to illustrate what orbitals the electrons occupy in an atom.ie: Nitrogen – 7 electrons
8 Electron Configurations electrons configurations (shorthand method) are a method of noting how many electrons are in an atom and where they are located.Order of FillingMaximum amount of electrons:s-orbital 2 electronsp-orbital 6 electronsd-orbital 10 electronsf-orbital 14 electronsQuantumSubshells
9 Example:Determine the electron configuration for the following elements:Lithium 3 electrons1s22s1Nitrogen 7 electrons1s22s22p3Neon 10 electrons1s22s22p6
10 Noble Gas Notationin order to write long configurations much easier we can use a noble gas configuration.In order to write a noble gas notation simply include the previous noble gas (in brackets) and list the electron configuration from the next element from the noble gas to the element you are determining the configuration for.Write the noble gas notation for Sodium[Ne]3s¹Write the noble gas notation for Sulfur[Ne]3s²3p⁴
11 Light behaves both as a wave and a particle. Properties of LightLight behaves both as a wave and a particle.Light’s Wavelike Propertiesvisible light is one kind of electromagnetic radiation.Light asa WaveElectromagnetic SpectrumPrism
12 all electromagnetic radiation moves at the speed of light (3 all electromagnetic radiation moves at the speed of light (3.00 x 108 m/s)Properties of WavesWavelength: (l) the distance between corresponding points on adjacent waves.2. Frequency: (n) the number of waves that pass a given point in one second.Frequency is measured in Hertz (Hz).
13 Speed of Light Equation What is the wavelength of radiation with a frequency of1.5 x 1013 Hz?Wavelength x 1.50 x 1013Hz = 3.00 x 108m/sWavelength = 3.00 x 108m/s / 1.50 x 1013HzWavelength = 2.00 x 10-5m
14 The Photoelectric Effect a phenomena involved with the emission of electrons from a metal when light shines on a metal.light of only a certain frequency enabled this event to occur light behaves like streams of particles!PhotoelectricEffectMax Plancksuggested that energy could only exist in discrete lumps called quantum.E = h nh = x JsPlanck andBlackbodyRadiationEinstein also proposed that light delivers its energy in chunks called photons.Therefore, in order for an electron to be ejected (photoelectric effect) , the electron must be struck by a single photon, of certain energy, to knock the electron loose.
15 One more question……….Are You Ready? The threshold photoelectric effect intungsten is produced by light of awavelength 260 nm. Give the energyof a photon of this light in joules.Find frequency!λ x ν = C260 nm x 1m/109 nm = 2.6 x 10-7 m2.6 x 10-7 m x ν = 3.0 x 108 m/sv = 1.15 x 1015/secE = h x νE = x 10-34Js x 1.15 x 1015/secE = 7.6 x J