Homework – Study! Prakash Rasie
Worksheet- http://static.schoolrack.com/files/115081/343339/Average_Atomic_Mass_Sheet.pdf
(There are also questions at the bottom)
Video to Help Explain- http://www.youtube.com/watch?v=ULRsJYhQmlo
Tips to remember: Don’t round until the end, or you can mess up the numbers. Go by multiplication/division rules for significant digits NOT addition/subtraction. Don’t forget to include the units.
Half-Life Worksheet- http://mrsbridgessciencepage.wikispaces.com/file/view/Half+life+problems+and+worksheet.pdf
Sig Fig Worksheet- http://misterguch.brinkster.net/PRA006.pdf
(There are also questions at the bottom)
Sig Fig Video- http://www.youtube.com/watch?v=6oj4y0d44nQ
Half-Life Video- http://www.youtube.com/watch?v=sqfRSJBhgfY
Video to Help Explain- http://www.youtube.com/watch?v=WWc3k2723IM
Worksheet- http://misterguch.brinkster.net/jan2006.pdf
Video to Help Explain- http://www.youtube.com/watch?v=2AFPfg0Como
Video to Help Explain- http://www.youtube.com/watch?v=IvSmfgxCSNQ
Worksheethttp://www.chemistryconnections.com/Periodic%20trends/Periodic%20Trends%20Worksheet.pdf
(There are also questions at the bottom)
Video to Help Explain- http://www.youtube.com/watch?v=G3qbooMh6Fc

Average Atomic Mass
1. The term “average atomic mass” is a _________________________average, and so is calculated differently from a “normal” average.
2. The element copper has naturally occurring isotopes with mass numbers of 63 and 65.
The relative abundance and atomic masses are 69.2% for a mass of 62.93amu and 30.8% for a mass of
64.93amu. Calculate the average atomic mass of copper.
3. Calculate the average atomic mass of sulfur if 95.00% of all sulfur atoms have a mass of 31.972 amu,
0.76% has a mass of 32.971amu and 4.22% have a mass of 33.967amu.
4. The four isotopes of lead are shown below, each with its percent by mass abundance and the composition of its nucleus. Using the following data, first calculate the approximate atomic mass of each isotope. Then calculate the average atomic mass of lead.
82p 82p 82p 82p
122n
1.37%
124n
26.26% 20.82%
125n
51.55%
126n
5. There are three isotopes of silicon. They have mass numbers of 28, 29 and 30. The average atomic mass of silicon is 28.086amu. What does this say about the relative abundances of the three isotopes?
6. Calculate the average atomic mass of bromine. One isotope of bromine has an atomic mass of
78.92amu and a relative abundance of 50.69%. The other major isotope of bromine has an atomic mass of 80.92amu and a relative abundance of 49.31%.
Significant Figures
1. How many significant digits are in the following measurements? a) 23.30 cm d) 0.0037 m b) 1843.02 g e) 705000 s c) 3.66 kg
2. Complete these addition problems. a) 6.201 cm + 7.4 cm + 0.68 cm + 12.0 cm = b) 1884 kg + 0.94 kg + 1.0 kg + 9.778 kg = c) 16. 156 g + 28.2 g + 0.0058 g + 9.44 g =

3. Complete these subtraction problems. a) 10.8 g – 8.264 g = b) 2104.1 m – 463.09 m = c) 16.50 mL – 8.0 mL =
4. Complete these multiplication problems. a) 10.19 m x 0.013 m = b) 3.2145 km x 4.23 km = c) (7.50 x 10 6 m)(2.2 x 10 -3 m) =
5. Complete these division problems. a) 80.23 m
2.4 s b) 4.301 kg
1.9 cm 3 c) 6.6 x 10 8 m
2.31 x 10 -2 s
Answers
1. a) 4 sd d) 2 sd
2. a) 26.3 cm
3. a) 2.5 g
4. a) 0.13m
2
5. a) 33 m/s
Periodic Trends b) 6 sd e) 3 sd c) 3 sd b) 1896 kg c) 53.8 g b) 1641.0 m b) 13.6 km 2 c) 8.5 mL c) 1.7 x 10 4 m 2 b) 2.3 kg/cm 3 c) 2.9 x 10 10 m/s
1)
2)
Rank the following elements by increasing atomic radius: carbon, aluminum, oxygen, potassium.
Rank the following elements by increasing electronegativity: sulfur, oxygen, neon, aluminum.

3)
4)
2)
3)
4)
5)
What is the difference between electron affinity and ionization energy?
Why does fluorine have a higher ionization energy than iodine?
5) Why do elements in the same family generally have similar properties?
Answers
1) Rank the following elements by increasing atomic radius: carbon, aluminum, oxygen, potassium.
From smallest to largest: oxygen < carbon < aluminum < potassium
Rank the following elements by increasing electronegativity: sulfur, oxygen, neon, aluminum.
From smallest to largest: neon < aluminum < sulfur < oxygen
What is the difference between electron affinity and ionization energy?
Electron affinity is a measure of the energy change that occurs when an atom grabs an electron. Ionization energy is a measure of how much energy it takes to pull electrons off of an element. Both values are for atoms in the gas phase.
Why does fluorine have a higher ionization energy than iodine?
It is harder to pull electrons off of fluorine because fluorine has a higher electronegativity than iodine. Iodine has a much lower electronegativity than fluorine because of the shielding effect, which states that the electrons in inner energy levels tend to push electrons in outer energy levels away from the nucleus. This pushing makes it harder for iodine to grab electrons.
Why do elements in the same family generally have similar properties?
Because they have similar electron configurations and the same number of valence electrons.
Because valence electrons are responsible for most of the chemistry we observe, this similarity causes the properties of the elements to also be similar.