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31 Cards in this Set
- Front
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Spectroscopic techniques are based on the same scientific principle, what is it? |
Under certain conditions, a substance can absorb or emit electromagnetic radiation in a characteristic way.
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ABSORPTION SPETRA: Outside the star's surface (the photosphere) a region called the chromosphere contains ions, atoms and small molecules. What do they do? |
The particles absorb some of the emitted radiation so that the light analysed from stars is missing certain frequencies. Absorption lines appear black as they are missing frequencies of light - they have been absorbed by particles in the chromosphere. This relates to the absorption spectra.
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EMISSION SPECTRA: When atoms, molecules and ions in the chromosphere absorb energy what happens? |
They are raised from their ground state to higher energy states called excited states. |
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When particles are raised from ground state to excited states how can they lose their extra energy? |
By emitting electromagnetic radiation. Emission spectra appear as coloured lines on a black background relating to the frequencies emitted. This relates to the emission spectra. |
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What is the hydrogen emission spectrum in visible light known as? |
Balmer series. |
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What is the hydrogen emission spectrum in ultraviolet light known as? |
Lyman series. |
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What is spectroscopy? |
The study of how light and matter interact. |
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What is the speed of light? |
3.00 x 10 to the power of 8 |
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What is the equation for the speed of light? |
Speed of light = wavelength x frequency (the speed of light is always constant) |
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The wave theory of light How does light behave like a wave? |
With a characteristic of wavelength and frequency |
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Particle theory of light How does light behave like a particle? |
In the way that light can be thought of as a stream of tiny packets of energy called photons. |
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What is the energy of the photon related to? |
The position of the light in the electromagnetic spectrum. |
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The wave and the photon models of light are linked..... |
Energy of a photon = Planck constant x frequency Value of Planck constant is 6.63 x 10 to the power of -34 |
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Bohr's theory Why do hydrogen atoms only emit a limited number of specific frequencies? |
When an atom is excited, electrons jump to higher energy levels - They will then drop back down to lower energy levels and emit the extra energy as electromagnetic radiation and giving off an emission spectrum. |
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Explain the absorption spectrum |
When white light is passed through a relatively cool sample of a gaseous element , black lines appear on an otherwise continuous absorption spectrum. The black lines on an absorption spectrum corresponds to light that has been absorbed by atoms in the sample. Electrons have been raised to higher energy levels without them dropping back again. |
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The sequence of lines in an atomic spectrum is characteristic of the atoms of an element - what can this be used to identify? What do intensities of lines provide? |
Used to identify the element, even when the element is present in a compound or is part of a mixture. A measure of the element's abundance |
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What are the three main points of Bohr's theory? |
1. The electron in the hydrogen atom exists only in certain definite energy levels or electron shells. 2. A photon of light is emitted or absorbed when the electron changes from one energy level to another. 3. The energy of the photon is equal to the difference between the two energy levels. |
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What colour does Lithium burn? |
Bright red |
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What colour does sodium burn? |
Yellow |
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What colour does potassium burn? |
Lilac |
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What colour does calcium burn? |
Brick red |
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What colour does barium burn? |
Apple green |
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What colour does copper burn? |
Blue green |
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An electron can only possess definite quantities of energy, what are these called? |
Quanta |
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What do the frequencies of lines of the Lyman series correspond to? |
Changes in electronic energy from various upper levels to one common lower level: level 1. Each line corresponds to a particular energy level change, for example level 4 to level 1. |
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In energy level diagrams, which are an alternative way of representing emission spectra, the larger the energy gap..... |
The higher the frequency of electromagnetic radiation emitted. |
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What does each arrow represent in an energy level diagram? |
An electron dropping from a higher energy level to a lower energy level. |
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Different colours of light will have different? |
Wavelengths |
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Recall the equation to link wavelength and frequency |
speed of light (ms-1) = wavelength x frequency |
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The wave and photon models of light are linked, recall the equation: |
energy of photon E (j) = Planck constant h (Js-1) x frequency v (s-1) |
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An electron's energy cannot change continuously, what does this mean? |
It is not able to change to any value, only those values which are allowed. |
