ELECTRONIC STRUCTURE OF ATOMS

ELECTRONIC STRUCTURE OF ATOMS - ELECTRONIC STRUCTURE OF...

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ELECTRONIC STRUCTURE OF ATOMS From Classical Physics to Quantum Theory
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CLASSICAL PHYSICS VS. QUANTUM THEORY CLASSICAL PHYSICS QUANTUM THEORY Can explain acceleration, projectiles and freely falling bodies Can be used to predict and explain certain macroscopic properties of molecules such as pressure Viewed energy as continuous and any quantity of which can be released. Cannot explain forces that hold atoms together Principles do not govern phenomena at atomic and molecular level Described molecules as bouncing marbles and balls (COLLAPSING ATOM PARADOX) Led to scientific proposals of epic proportions New era in Physics started in 1900s by Max Planck Can be understood by the nature of waves Max Planck devised a relationship between energy and frequency.
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PROPERTIES OF WAVES WHAT IS A WAVE? Vibrating disturbance by which energy is transmitted. PROPERTIES OF WAVES PROPERTY DEFINITION SYMBOL UNITS FREQUENCY No. of peaks passing per second ν m/s, cm/s, nm/s AMPLITUDE Peak height above midline A Varies with type of wave WAVELENGTH Peak to peak distance λ m, cm, nm SPEED Distance per time u/c *c for speed of light Cycle/s, Hertz
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ELECTROMAGNETIC RADIATION In 1865, James Clerk Maxwell proposed that visible light is composed of electromagnetic waves(radiation). This radiation is composed of oscillating electric and magnetic fields, perpendicular to each other and to the direction of the travel.
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ELECTROMAGNETIC RADIATION Speed of electromagnetic waves is equal to the speed of light which is 3 x 10 m/s(vacuum) Electromagnetic radiation is emission and transmission of energy in the form of electromagnetic waves. These types of waves can be emitted or absorbed by atoms. This principle is known as Maxwell theory. 8
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ELECTROMAGNETIC RADIATION
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PLANCK’S QUANTUM THEORY Electromagnetic radiation is emitted over wide range of wavelengths when solids are emitted. Planck gave the name quantum to the smallest quantity of energy that can be emitted or absorbed in the form of electromagnetic radiation The energy, E of a single quantum is E = h ν where h = Planck’s constant, 6.63 x 10 J -s Quantum Theory states that energy is transmitted in multiples of h ν -34
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PHOTOELECTRIC EFFECT In 1905, Albert Einstein used the concept of Quantum Theory to explain photoelectric effect. Einstein asserted that light consisted of bundles of energy that can carry and transfer energy like particles paving the way to the concept of wave-particle duality.
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BOHR’S THEORY OF HYDROGEN ATOM Niels Bohr explained emission spectrum of H atom(earned him Nobel Peace Prize for Physics) Continuous or line spectra of radiation is emitted by excited substance. Bohr postulated that
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ELECTRONIC STRUCTURE OF ATOMS - ELECTRONIC STRUCTURE OF...

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