4 EMRElectromagnetic Radiation: Electromagnetic radiation is one of the ways in which energy travels through space. All forms of EMR compose the electromagnetic radiation spectrum, which includes sun rays, microwaves, X- rays, visible spectrum, UV rays and IR rays.Some characteristics of EMR are:All electromagnetic radiation moves at a constant speed of about 3.0 X 108 m/s.All EMR exhibit wave like behavior. Waves have three primary characteristics:Wavelength: It is the distance between two consecutive peaks or troughs in a wave.Frequency: It indicates how many waves pass a given point per second.Speed: It indicates how fast a given peak is moving through the space.Speed of light ,c=ln ,where l=wave length and n =frequency
6 Refer to the following EMR spectrum. (visible spectrum Roy G. BiV) Imagine you have invented a machine that allows you to see all types of EMR. Make a list of type of EMR you might see in your home.What will happen if you change the red light in the dark room for photo processing with the yellow light and why?
7 Wave Nature of LightBefore the concept of quantization of energy, the wave like nature of light/energy was widely accepted.Two properties that exhibit the wave like behavior of light are interference and diffraction.Animation Diffraction:Animation for Interference:
9 Planck’s Theory of Quantization of Energy To explain this, Planck suggested that the energy transfer or exchange is not a continuous process, but is done in small packets of energy called by him as quantum.(Word quantum means fixed amount.) So, he introduced the concept of quantization of energy.According to Planck’s theory, E= hv,where E= energy of radiationh= Planck’s constantv= frequency of radiationPlanck’s theory: Before Planck’s theory, the wave model of the light was widely accepted. But it was unable to explain some phenomenon for example change in the radiation (wave length) emitted by an object with the change in temperature.
10 Quantization of Energy: Max Plank wwwWhere else do you see quantization in real life?
14 Photoelectric Effect: It refers to the emission of electrons from a metal, when the light shines on the metal. For each metal the frequency of light needed to release the electrons is different. But the wave theory of light could not explain it. The photoelectric effect led scientists to think about the dual nature of light i.e. as a wave and a particle both.Animation 1:Animation 2:
15 Dual Wave- Particle Nature of Light Dual nature (Wave- Particle nature) of light: Albert Einstein in 1905, expanded on Planck’s theory by introducing the idea of the dual nature of the radiation. Albert Einstein called the quantum of energy in light as ‘photons’.Light as wave Light as particle DUAL NATURE OF LIGHT
16 http://www. nobel. se/physics/educational/tools/quantum/w-p-images/wp Photoelectric EffectMax Planck suggested that the hot object emits energy in small, specific amounts called quanta.1905, Einstein said electromagnetic radiation has a dual wave- particle nature.
18 Continuous and Line Spectra (Absorption and Emission Spectrum- Line Spectra) (bsorption.html&h=240&w=450&sz=33&hl=en&start=2&tbnid=TaN57QO8MhMG4M:&tbnh=66&tbnw=124&prev=/images%3Fq%3Dabsorption%2Band%2Bemission%2Bspectrum%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DN)
19 Bohr Model Of the Hydrogen Atom The energy levels of Hydrogen ( As explained by Bohr’s Model) :An excited atom can release some or all of its excess energy by emitting a photon, thus moving to a lower energy state.The lowest possible energy state of an atom is called the ‘ground state’.Different wavelengths of light carry different amount of energy per photon. Ex. A beam of red light has a lower energy photons than beam of blue light.Ephoton=hv
23 Light Equations E=h n E is energy (in joules) c= l nc is the speed of light (3.0 x 108 m/s)lambda is the wave length (in m, cm, or nm)n represents the frequency (waves/s or hertz)E=h nE is energy (in joules)h is Planck’s Constant (h= x 10-34J s)n is frequencyE=h(c/ l)
24 Dual Wave-Particle nature by De Broglie Quantum Theory: Describes mathematically the wave properties of electrons or other very small particles treating e as waves and using Heisenberg’s and De Broglie’s principles.. Heisenberg Uncertainty Principle: States that it is impossible to determine simultaneously both the position and velocity of an electron or any other particle.Dual Wave-Particle nature by De Broglie
25 Quantum Mechanical Model of Atom (Schrodinger’s Model) Erwin Schrödinger, in developing a quantum-mechanical model for the atom, began with a classical equation for the properties of waves. He modified this equation to take into account the mass of a particle and the de Broglie relationship between mass and wavelength. The important consequences of the quantum-mechanical view of atoms are the following: (The energy of electrons in atoms is quantized.The number of possible energy levels for electrons in atoms of different elements is a direct consequence of wave-like properties of electrons.The position and momentum of an electron cannot both be determined simultaneously.The region in space around the nucleus in which an electron is most probably located is what can be predicted for each electron in an atom. Electrons of different energies are likely to be found in different regions. The region in which an electron with a specific energy will most probably be located is called an atomic orbital.
35 Principle energy level (n) Type of sublevel Orbitals and Electron Capacity of the First Four Principle Energy LevelsPrinciple energy level (n)Type of sublevelNumber of orbitals per typeNumber of orbitals per level(n2)Maximum number of electrons (2n2)1s248p3918d51632f7
54 Quantum Number Terms Ground State: Lowest energy state of an atom Excited State: A state in which an atom has a higher potential energy then it has in its ground stateOrbital: A 3D region around the nucleus that indicates the probable location of an electronQuantum Numbers: Specify the properties of atomic orbitals and the properties of electrons in orbitalsPrinciple Quantum Number: (n) Indicates the main energy level occupied by the electron.Angular Momentum Quantum Number: (l) Indicates the shape of the orbital.Magnetic Quantum Number: (m) Indicates the orientation of an orbital around the nucleus.Spin Quantum Number: (+1/2, -1/2) Indicates the two fundamental spin states of an electron in an orbital
55 Electron Configuration Theories Electron Configuration TheoriesHund’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.Aufbau’s Principle: An electron occupies the lowest-energy orbital that can receive it.Pauli’s Exclusion Principle: No two electrons in the same atom can have the same set of four quantum numbers.
56 Ways to Represent Electron Configuration Expanded Electron ConfigurationCondensed Electron ConfigurationsOrbital NotationElectron Dot StructureWrite the above four electron configurations for Zinc, Zinc ion and Cu ion.