* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Quantum Theory of the Atom
Survey
Document related concepts
Hydrogen atom wikipedia , lookup
Atomic orbital wikipedia , lookup
Electron configuration wikipedia , lookup
Double-slit experiment wikipedia , lookup
Particle in a box wikipedia , lookup
X-ray photoelectron spectroscopy wikipedia , lookup
Ultraviolet–visible spectroscopy wikipedia , lookup
Ultrafast laser spectroscopy wikipedia , lookup
Electron scattering wikipedia , lookup
Tight binding wikipedia , lookup
Astronomical spectroscopy wikipedia , lookup
Atomic theory wikipedia , lookup
X-ray fluorescence wikipedia , lookup
Matter wave wikipedia , lookup
Theoretical and experimental justification for the Schrödinger equation wikipedia , lookup
Transcript
Models, Waves, and Light Models of the Atom • Many different models: – Dalton-billiard ball model (1803) – Thompson – plum-pudding model (1897) – Rutherford – Nuclear model of the atom (1911) – Bohr – uses quantized energy of the atom (1913) – Quantum Mechanical Model of the Atom (1926) • Each new model contributed to the model we use today. • Even our current model, does not give us an exact model of how electrons interact. Quantum Mechanical Model of the Atom • Quantum Mechanical Model is the current description of electrons in atoms -does not describe the electron’s path around the nucleus • Quantum Mechanical Model is based on several ideas -Schrodinger wave equation (1926) treats electrons as waves. -Heisenberg uncertainty principle (1927) states that it is impossible to know both the velocity and position of a particle at the same time. Atomic Emission Spectrum •When a current is passed through a vacuum tube of gas at low pressure, a set of frequencies of the electromagnetic waves are emitted by atoms of the element •Used to determine which elements are present in a sample •Used to determine which elements are present in a star •Each element has a unique spectrum •Only certain colors are emitted meaning only certain frequencies of light are emitted • A spectroscope that has a diffraction grating is needed to see the atomic emission spectra, which acts similar to a prism, separating different frequencies of light Explanation of Atomic Spectra •Electrons start at their lowest energy level (ground state) •When an electron absorbs energy it moves to a higher energy level (excited state) •When an e- drops back down to a lower energy level it gives off a quantum of energy called a “photon” •Only certan atomic spectra are possible and emitted Step 2 Step 1 Photons • Behaves like a particle • Behaves like a wave Electromagnetic Spectrum • Electromagnetic spectrum is the range of all energies emitted from photons acting like waves. • If it is not in the visible light range, it may be giving off other forms of electromagnetic radiation like radio, microwaves, infrared, ultra violet, x-rays, or gamma rays. • Used to determine which elements are present in a star (because stars are gases) Electromagnetic Spectrum with Visible Light Spectrum How do Neon Signs work? • They have “excited” gases in them. Characteristics of a Wave • Wavelength (lambda) – shortest distance between equivalent points on a continuous wave [Unit = meters] • Frequency (nu) – the number of waves that pass a given point per second [Unit = 1/second = s-1 = Hertz (Hz)] • Crest – Highest point of a wave • Trough – Lowest point of a wave • Amplitude (a)– height from its origin to its crest (highest point) or trough (lowest point) (Wavelength) Amplitude Amplitude (Wavelength) Wavelength and Frequency • Wavelength () and frequency () are related • As wavelength goes up, frequency goes down • As wavelength goes down, frequency goes up • This relationship is inversely proportional Wavelength and Frequency cont. c = = c / =c/ c Speed of light wavelength frequency c = 8 Speed of light (c) = 3 x 10 m/s Practice 1: • Calculate the wavelength () of yellow light if its frequency () is 5.10 x 1014 Hz. **Hz = 1/s =c÷ = 3 x 108 m/s ÷ 5.10 x 1014 Hz -7 = 5.88 x 10 m c Practice 2 • What is the frequency () of radiation with a wavelength () of 5.00 x 10-8 m? What region of the electromagnetic spectrum is this radiation? =c÷ 8 -8 = 3 x 10 m/s ÷ 5.00 x 10 m = 6.00 x 1015 1/s c ultraviolet region (just barely) How Much Energy Does a Wave Have? E • • • • • • Energy of a wave can be calculated Energy Use the formula E= h h Planck’s constant frequency E= Energy, = frequency h = Planck’s constant = 6.626 x 10-34 Joule . Sec Joule is a unit for energy (J) Energy and frequency are directly proportional, as frequency increases, energy increases Practice 3 • Remember that energy of a photon given off by an electron is E =h • How much energy does a wave have with a frequency of 2.0 x 108 s-1? ( h = 6.626 x 10-34 Js) E =h E = (6.626 x 10-34 Joule s)(2.0 x 108 s-1) E = 1.3 x 10-25 Joule Visible Light, Frequency, and Energy • Red: longest wavelength (), smallest frequency () • Red: frequency smallest (), least amount of energy (E) • Violet: smallest wavelength (), largest frequency () • Violet: frequency largest (), greatest amount of energy (E)