《大学化学 Chemistry》课程PPT教学课件（英文）Chapter 5 Atomic Models

Chapter 5 Atomic Models Different metal containing compounds emit colored light when fireworks burn. This colored light is a combination of a series of colors called a spectral pattern(谱带) Each element emits its own characteristic spectral pattern, which can be used to identify the element. This allowed the scientists in 1900s to develop models of the atoms internal structure

Chapter 5 Atomic Models Different metal containing compounds emit colored light when fireworks burn. This colored light is a combination of a series of colors called a spectral pattern. (谱带) Each element emits its own characteristic spectral pattern, which can be used to identify the element. This allowed the scientists in 1900s to develop models of the atom’s internal structure

5. 1 Models help us visualize the invisible world ofatoms Atom is very small in Ping-Pong ba in the Earth

5.1 Models help us visualize the invisible world of atoms Atom is very small

We can not see them in the usual sense This is because light travels in waves and atoms are smaller than the wavelengths of visible light, which is the light that allows the human eye to see things So we can not see atoms through the media of light, even with a microscope light An atom A bacterum 10m m

We can not see them in the usual sense. This is because light travels in waves and atoms are smaller than the wavelengths of visible light, which is the light that allows the human eye to see things. So we can not see atoms through the media of light, even with a microscope

We can see atoms indirectly through scanning tunneling microscope(STM), which was invented in 1980s figl: Scanning tunne ling microscope ig3: an STM image of mono Fig2: an image of gallium layer of perylene derivativ and arsenic atoms graphite substrate, where the obtained with an STm epitaxial relationship is observed between the organic molecule and the substrate graphite

We can see atoms indirectly through scanning tunneling microscope (STM), which was invented in 1980s. fig3 : an STM image of mono￾layer of perylene derivative on graphite substrate, where the epitaxial relationship is observed between the organic molecule and the substrate graphite Fig1:Scanning tunneling microscope Fig2:an image of gallium and arsenic atoms obtained with an STM

5.2 Light is a form ofenergy Wavelength(nm 10 1016 requency(Hz) Gamma X rays Ultra Infrared Microwave Radio waves violet Type of radiation X ray Sun lam Heat Microwave ovens, UHF TV FM radio lamps police rad satellite stations 400nm

5.2 Light is a form of energy

5.3 Atoms can be identified by the light they emit When we view the light from glowing atoms, we see that the light consists of a number of discrete frequencies rather than a continuous spectrum This is called element' s atomic spectrum(原子 Btv). In 1800s researchers noted the orderliness of elements atomic spectrum, especially hydrogen, but could not give the explanation

5.3 Atoms can be identified by the light they emit When we view the light from glowing atoms, we see that the light consists of a number of discrete frequencies rather than a continuous spectrum. This is called element’s atomic spectrum (原子 光谱). In 1800s researchers noted the orderliness of element’s atomic spectrum, especially hydrogen, but could not give the explanation

氢原子光谱 抽掉放电管中的空乞,充入小量氪乞 通高压电流

氢原子光谱

5.4 Niels bohr used the quantum hypothesis to explain atomic spectra Max Planck's quantum hypothesis(量子假设) a beam of light energy is not the continuous stream of energy, but consists of small, discrete packets of energy. Each packet was called a quantum. In 1905, Einstein recognized that these quanta of light behave like particles. Each quantum was called a photon(光子) ) Light behaves as both a wave and a particle Totally reflecting mirror Flash lamp Laser beam Partially reflecting mi rror

5.4 Niels Bohr used the quantum hypothesis to explain atomic spectra Max Planck’s quantum hypothesis (量子假设): a beam of light energy is not the continuous stream of energy, but consists of small, discrete packets of energy. Each packet was called a quantum. In 1905, Einstein recognized that these quanta of light behave like particles. Each quantum was called a photon (光子). Light behaves as both a wave and a particle

Electr Bohr's explanation potential energy and moves closer Electron gai to nucleus. a potential hoton of pl energy ar d Electron light is moves farther High potential emitted from nucleus energy A photon of light is absorbed Low potential energy Nucleus Nucleus

Bohr’s explanation Electron loses potential energy and moves closer to nucleus. A photon of light is emitted Electron gains potential energy and moves farther from nucleus. A photon of light is absorbed

Bohr's planetary model of atom There are only a limited number of permitted Photon energy levels in an atom and an electron can onl stay in these energy levels Each energy level has a n=1 principal quantum n=2 number n(主量子数 The energy level with n=l has the lowest eners

Bohr’s planetary model of atom There are only a limited number of permitted energy levels in an atom, and an electron can only stay in these energy levels. Each energy level has a principal quantum number n ( 主 量子数). The energy level with n=1 has the lowest energy