8/2/2023 0 Comments Periodic table quantum numbersFigure 8.05 “Bohr’s Model of the Hydrogen Atom” shows a model of the hydrogen atom based on Bohr’s ideas. This means that only certain frequencies (and thus, certain wavelengths) of light are emitted. Finally, Bohr suggested that the energy of light emitted from electrified hydrogen gas was equal to the energy difference of the electron’s energy states: Because the energies of the electron can have only certain values, the changes in energies can have only certain values (somewhat similar to a staircase: not only are the stair steps set at specific heights but the height between steps is fixed). Bohr suggested that the energy of the electron in hydrogen was quantized because it was in a specific orbit. Quantities that have certain specific values are called quantized. He suggested that the electron in a hydrogen atom could not have any random energy, having only certain fixed values of energy that were indexed by the number n (the same n in the equation above and now called a quantum number). In 1913, the Danish scientist Niels Bohr suggested a reason why the hydrogen atom spectrum looked this way. Figure 8.04 “Hydrogen Spectrum.” The spectrum of hydrogen was particularly simple and could be predicted by a simple mathematical expression. Where n = 3, 4, 5, 6,…, but they could not explain why this was so. Late-nineteenth-century scientists found that the positions of the lines obeyed a pattern given by the following equation: Particularly simple was the spectrum of hydrogen gas, which could be described easily by an equation no other element has a spectrum that is so predictable (Figure 8.04 “Hydrogen Spectrum”). Why does the light emitted from an electrically excited gas have only certain colours, while light given off by hot objects has a continuous spectrum? For a long time, it was not well explained. Here are the colours of light in the line spectrum of Hg. (b) However, when electricity is passed through a gas, only certain colours of light are emitted. Figure 8.03 “Prisms and Light.” (a) A glowing object gives off a full rainbow of colours, which are noticed only when light is passed through a prism to make a continuous spectrum. It turns out that every element has its own unique, characteristic line spectrum. However, when electricity is passed through a gas and light is emitted and this light is passed though a prism, we see only certain lines of light in the image (part (b) in Figure 8.03 “Prisms and Light”). This image is known as a continuous spectrum. We notice this when the visible portion of the electromagnetic spectrum is passed through a prism: the prism separates light into its constituent colours, and all colours are present in a continuous rainbow (part (a) in Figure 8.03 “Prisms and Light”). Incandescent lights and fluorescent lights generate light via these two methods, respectively.Ī hot object gives off a continuum of light. There are two fundamental ways of generating light: either heat an object up so hot it glows or pass an electrical current through a sample of matter (usually a gas).
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