Drop back to your ground state you have to emit a

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drop back to your ground state you have to emit a photon of light that has the same energy as it took to move you to an excited state. The energy is always in specific energy packets called quanta , which correspond to the energy difference between the two orbits. When a gaseous element is heated in a vacuum tube, it gives off light in certain specific wavelengths. This is called an emission spectrum . The emission spectrum is a fingerprint of the element. See page 292 for the emission spectrum of hydrogen, helium, and neon. Ionization What would happen if you kept adding energy to the electron? It would keep moving to higher energy levels. But, there are not infinite energy levels. It is possible to remove an electron from an atom. This is called ionization . Ionization energy is defined as the energy required to remove an electron from an atom in its ground state. When an electron is removed from an atom the remaining charged particle is called an ion. When an atom loses an electron the resulting ion is positively charged. It is also possible to force an atom to absorb an electron, resulting in a negatively charged ion. We will discuss this later. Bohr Atoms and Valence Electrons Bohr’s theory said that there were distinct energy levels in an atom. These levels are called shells . Each shell can only hold a certain number of electrons. And, each shell does not hold the same number of electrons. For example, the first shell can only hold two electrons, but the second can hold eight, and the sixth holds thirty two. Bohr saw the energy levels around the nucleus of the atom to be like orbits around a planet. This isn’t quite how it works. Bohr also said that the electrons in the outermost energy level were valence electrons , these are the electrons that are the most likely to be ionized. The valence electrons will always be in the outer most shell, the valence shell . They are the part of the atom that interacts with the rest of the world. The nucleus and any internal electrons ( kernel ) are shielded by the valence shell. The electrons that are not in the outermost principle shell are called core electrons. The valence electrons are where chemistry happens. The chemical properties of elements are largely determined by the number of valence electrons they contain. The great success of the Bohr model of the atom is that it predicts the lines of the hydrogen emission spectrum. However, it fails to predict the emission spectrum of any element with more than one electron. The Quantum Mechanical Model Alright, Bohr was on the right track, but he wasn’t there yet. Along came a French physics graduate student named De Broglie. He said that if light photons (which are waves) can, at times, act like particles, then why can’t electrons (which are particles) occasionally act as waves? He was right. The electrons in the shells were not acting as objects in orbit around a
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center of mass but rather as a light beam. The electrons exhibit wave-particle duality , just like photons. The electron does not exist as a particle that you can say “There it is, right there.” It exists as a probability. It’s like that sweater in your closet. You know it’s in the closet, but you
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