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Worksheet: Light & Atoms (Introduction)
Work on these problems as practice. You may use a room copy of a chemistry book as a reference. There will be a Quizlette over the
new ideas next time.
Light & Atom Ideas
1. A version of the electromagnetic spectrum is shown to the right 
a) ____________________________ What is the approximate wavelength of red light in meters?
b)
____________________________ Estimate the approximate frequency of x-rays.
c) ____________________________ If the spectrum were drawn to scale, which section would stretch out
the farthest?
d)
____________________________ Which has higher energy, blue light or red light?
e)
____________________________ Which has lower energy, microwave or ultraviolet light waves?
f)
As the frequencies of light get larger, how do the matching wavelengths change?
g) ____________________________ The wavelength and frequency of a wave are related by: velocity of a
wave = wavelength • frequency; [v=ƒ • ]Pick two values from the chart and calculate the
approximate speed of a light-wave.
h) ____________________________ The actual speed of light is 3.0x108 m/s. Using this value, calculate the
frequency of a light wave with a wavelength of 6x10-8 m. What type of wave is this?
2. In the Ring of Truth: Atoms video, they demonstrated how electrons at high energy levels give
off light as they fall down to lower levels.
a) ____________________________ Which transition (I, II or III) would give off light of the highest energy?
b) ____________________________ Which transition (I, II or III) would give off light of the lowest
frequency?
c)
____________________________ Which transition would give off light of the longest wavelength?
d)
How many different light emissions (“colors”) would this atom produce?
e)
The energy of electrons around an atom are quantized. What does this mean?
Worksheet: Atoms and Light
1
5/12/2017
Isotope Review
3. Boron occurs naturally as two main isotopes: 10B [19.80%] and 11B [80.20%].
a)
____________________________ How many neutrons does 11B have?
b)
____________________________ How many electrons does an neutral atom of 10B have?
c)
____________________________ Calculate the atomic weight of boron based on this information.
d) The actual mass of 10B is 10.01 amu, even though it is made of a specific number of protons and neutrons. Why isn’t it the whole
number 10?
4. ____________________________ In pre-AP chemistry a student’s grade is based on three categories: daily practice work (20% of the grade),
experiments (25%) and tests (55%). If a student has the following category grades: daily=95, experiments=92 and tests=80, calculate
what her course percentage would be. What letter grade would this be?
5.
____________________________ Find the average atomic mass (also known as the atomic weight) of sulfur from a periodic table.
b)
____________________________ If you had 6.02x1023 atoms of this, how many grams would that be?
c)
____________________________ What is the mass, in grams, of one atom of sulfur?
6.
Why don't scientists weigh out individual atoms in lab when working on experiments?
7.
a)
The atomic weight of lithium is 6.941.
Why isn’t this value a whole number (such as 7?)
b) Lithium comes in two main isotopes, one with three neutrons and one with four. Which one is most common? Explain your
choice.
General Review — Expect to see these topics on future tests or quizzes
8.
____________________________ A solid has a density of 344-g/cm3. Determine the volume of 1.0899-g of this compound.
9.
____________________________ A gas has a density of 2.3x10-3 g/cm3. Calculate the mass of 4.0x103cm3 of this substance.
10. Change these numbers into scientific notation or to decimal (“normal”) format. Keep the same number of significant figures.
a.__________________________ 23,000
f. ______________________ 1.2x105
b. _________________________ 340
g. ______________________ 4.500x10-4
11. When determining the thickness of aluminum foil, some students used a very large piece to weigh and then measure for density.
Why would this procedure generally give a more accurate result than using a very small piece?
Worksheet: Atoms and Light
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5/12/2017