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1. a) Atoms like to emit and absorb (1 word) of particular frequencies. Which frequencies are favored depends on the   (3 words) .

b) An atom consists of a heavy (1 word) surrounded by light (1 word).

c) A    (1 word) atom has one electron besides its nucleus. A helium atom has a heavier nucleus and (1 word) electrons. A lithium atom has a still heavier nucleus and (1 word) electrons. An (1 word) atom has eight electrons.

2. a) Not all of the (1 word) are allowed for the (1 word) in an atom or molecule. The (1 word) can have only certain energies which are usually measured in  (2 words), abbreviated eV.) The (2 words) can be illustrated with a diagram:

b) The example shown above is for (1 word), but each kind of atom or molecule has its own energy level structure. This picture shows the four (1 word) energy levels. There are more.

c) For any energy above the blue line, i.e. greater than (value and unit), the only electron in the hydrogen atom becomes  (2 words) which means it is not attached to the atom any more. The (1 word) energy corresponds to (1 word) the electron from the hydrogen atom.

 3. a) An atom in one of its (1 word) levels can get to a (1 word) level by emitting a (1 word).

b) The energy is carried away by the (1 word) and thus is given by the difference:

Energy of emitted   (1 word) = ( (1 word) energy before) - ( (1 word) energy after)

  1.88 eV = (values with units)

 In this case, the energy of 1.88 eV corresponds to a wavelength of  (value with unit), which is red and is called (1 word) light.

4. a) An atom in its ground state or in one of its excited states can absorb a passing photon of the right energy and be raised to a (1 word) energy state:

Note that the passing photon has to be just the right color or it can't be (1 word).

b) Energy of (2 words) = (atom energy (1 word)) - (atom energy (1 word))

We can use a simpler picture with arrows to illustrate these processes:

5. a) Isolated atoms can (1 word) or (1 word) packets of electromagnetic radiation having (1 word) energies dictated by the detailed atomic structure of the atoms.

b) After being passed through a prism or a diffraction grating, the corresponding spectrum may exhibit a (1 word), or may have superposed on the continuum bright lines (an  (2 words) or dark lines (an (2 words) , as illustrated in the following figure.

6. The origins of these three types of spectra are illustrated in the following figure.

b) But if you look at a thin, transparent gas, then you can see photons that come to you directly from an (1 word) atom.

A hot gas (1 word) photons with the characteristic wavelengths corresponding to the (5 words) of the atoms or molecules in the gas. This leads to (2 words) in the spectrum.

d) When an (2 words) is passed through a glass tube that contains hydrogen gas at (1 word) pressure the tube (2 words)  blue light. When this light is passed through a prism (as shown in the figure below), four narrow bands of bright light are observed against a (1 word) background. This is an   (1 word) spectrum.