Chemistry Sch3U - Unit 1

Topics: Atom, Chemical bond, Periodic table Pages: 10 (2614 words) Published: December 27, 2012
Chemistry SCH3U
Unit 1
Lesson 1

Key Questions

1. List three physical properties and one chemical property of
a) an iron nail
* conducts heat and electricity well
* solid at room temperature
* ductile
* rusts in water (chemical)
b) gasoline
* liquid at 20deg C
* boils between 20 and 200 degrees Celsius
* not soluble in water
* flammable in the presence of oxygen (chemical)

2. People in a workplace should have access to MSDS sheets so that * chemicals can stored properly
* chemicals can be handled properly
* the situation of improper storage or handling can be dealt with quickly and safely

3.a) The atomic mass of an element on the periodic table is an average of the masses of the naturally-occurring isotopes. b) According to the periodic table, the average mass of boron is 10.8u. c) With an average mass of 10.8, and the choice being either boron-10 or boron-11, boron-11 should be most common because it is the nearest isotope to the average mass.

4. Round each number to the given number of significant digits. a) 1.160 (two significant digits) 1.2
b) 0.002 305 (three significant digits) 0.002 31
c) 12 040 (three significant digits) 12 000

5. Write the answer to each calculation using the correct number of significant digits. a) 12.6 mL – 2.03 mL = 10.6 mL
b) 10.0 g / 2.4 mL = 4.2 g/mL
c) 125 Aspirin tablets X 1.3 g / tablet = 162.5 g = 160 g

6. Complete the following table.
Particle| Mass of subatomic particle (g)| Charge of subatomic particle| Location in atom| proton| 1.67 x 10^-24| positive| nucleus|
electron| 9.11 x 10^-28| negative| outside the nucleus| neutron| 1.67 x 10^-24| neutral| nucleus|
7. Complete the following table by filling in the boxes with the appropriate information for the neutral elements. Name of isotope| Atomic number| Mass number| Number of protons| Number of electrons| Number of neutrons| hydrogen-1| 1| 1| 1| 1| 0|

boron-11| 5| 11| 5| 5| 6|
magnesium-12| 12| 24| 12| 12| 12|
zinc-68| 30| 68| 30| 30| 38|
tin-119| 50| 119| 50| 50| 69|
silicon-30| 14| 30| 14| 14| 16|
8. Compare the sizes of the elements in each pair by referring to your periodic table. State which element has a larger atomic radius, and explain your reasoning. a) Ca and Se Calcium has a larger atomic radius because it has less protons, and less pull on nearby electrons, thus the calcium atom is less compressed than the selenium atom. b) N and P Phosphorus has a larger atomic radius because it has an additional energy level, meaning that the valence electrons are farther from the nucleus, and thus suggesting that the atomic radius is greater than that of nitrogen.

9. Carbon has a higher first ionization energy than lithium because the carbon atom has more protons and a stronger hold on its valence electrons. The lithium atom is larger than the carbon atom, which indicates that its first ionization energy is lesser. Lastly, metal atoms generally have a lower Eion than non-metals. ELABORATE BOTHE REASONS: Reason # 1Carbon has a higher first ionization energy than lithium because it has a smaller atomic radius and a higher positive nuclear charge. The higher positive nuclear charge results in a greater force of attraction on the electrons and, in fact, its smaller atomic radius. This stronger hold on the electrons means it takes more energy to knock free its outermost electrons. REASON # 2. Lithium wants to lose the one electron it has in its outermost energy level, because in doing so, it achieves the same stable electron arrangement as the nearest noble gas, He. Therefore, the removal of the outermost electron in lithium does not require a lot of energy, hence the lower ionization energy. Carbon, on the other hand, will need to lose four electrons from its outermost energy level in order to achieve a stable electron arrangement of helium gas. Its outermost energy level is...
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