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Mrs. Smith
Chemistry Unit 2 –Essential Knowledge
Topic
Elements and the
Periodic Table
1.2
(You must know everything in Unit 1 and add to it the following information)
Essential Knowledge
Atoms are made of three types of subatomic particles: protons, neutrons and electrons. Each atom has a nucleus
in the center, made of protons and neutrons packed tightly together. An electron cloud surrounds the atomic
nucleus.
A proton has a positive charge and a relative mass of one. The atomic number for an element is the same as the
number of protons. All atoms of the same element have the same number of protons.
An electron has a negative charge and a relative mass of zero. The number of electrons is the same as the
number of protons in a neutral atom.
A neutron has no charge and a relative mass of one.
Atoms are electrically neutral meaning they have the same number of protons as electrons.
Know the contributions and sequence of the development of the modern atomic theory from Democritus (p. 101),
John Dalton (p.102), JJ Thompson (p. 104), Robert Milikan (p.105), Ernest Rutherford (p. 107), Niels Bohr
(p.128) and Erwin Schrodinger (Quantum Mechanical Model) p.130.
Problem Set 1.1 Read Chapter 4 and Chapter 5 pp.127-132
Compounds and
Bonding
2.2
Describe and Learn the Contributions to the Modern Atomic Model of the following scientists and models.
Please include the years in which they lived in your description of the scientists.
a. Democritus
b. John Dalton
c. JJ Thompson
d. The Plum Pudding Model e. Ernest Rutherford
f. The Nuclear Model
g. The Gold Foil Experiment
1. A sample of copper with a mass of 63.5 grams contains 6.02 x 10 23 atoms. Calculate the mass of a single
copper atom.
2. Calculate the atomic mass of bromine. The two istopes of bromine have atomic masses and relative abundance
of 78.92 amu (50.69%) and 80.92 amu (49.31%) Show your work and calculate to the correct number of
significant figures:
4. How can there be more than 1000 different atoms when there are only about 100 different elements?
5. What data must you know about the isotopes of an element to calculate the atomic mass of the elements?
6. Make a table that includes the three different particles of the atom that includes: symbol, charge, mass, and
location in the atom.
7. What parts of Dalton’s atomic theory no longer agree with the current picture of the atom?
8.. Dalton’s atomic theory was not correct in every detail. Should this be taken as criticism of Dalton as a
scientist? Explain.
9. What was inadequate about Rutherford’s model of the atom?
10. What did Bohr assume about the motions of electrons?
Subscripts in a chemical formula represent the relative number of each type of atom. The subscript always
follows the symbol for the element. The subscripts indicate the ratio elements (in terms of atoms or moles) in the
compound.
Example: In a water molecule, H2O, there are 2 hydrogen atoms and 1 oxygen atom. This
means
that two moles of hydrogen combines with exactly one mole of oxygen.
Parentheses are used when a subscript affects a group of atoms.
Example: the formula for magnesium nitrate is written Mg(NO3)2 to show that there is a ratio of one magnesium
atom, 2 nitrogen atoms and 6 oxygen atoms in the compound.
Problem Set 2.1
Kinetic Theory
3.2
1. Make a table that includes the number of atoms in the compound and the number of atoms of each element in
the comounds.
a. Ba(OH)2
b. Cu(NO3)2
c. (NH4)3 PO4
d. NaCl
e. K2SO3
f. Fe2O3
g. NH4Br
h. Mg(C2H3O2)2
i. KNO3
j. Cu3(PO4)2
k. CH3OH
l. CH3(CH2)3OH
Solids have a fixed shape. In a solid the particles are closely packed together. Each particle in a solid is held in
one position and vibrates around that position. This results in a definite shape and volume.
The particles in a liquid stay relatively close together, but they can move around each other (rotate or
tumble). This results in a definite volume but no definite shape.
Gas particles are far apart; they move rapidly and collide with each other and with the walls of the container.
This random motion results in no definite shape or volume.
Phase changes (changes in physical state) occur when particles either speed up or slow down changing their
relative motions. For a given substance, freezing and melting occur at the same temperature. Boiling and
condensing also occur at the same temperature. For example, water both freezes and melts at 0oC (and both boils
and condenses at 100oC). Which phase change takes place depends on whether heat (energy) is being added or
removed.
Problem Set 3.1
Read Pages 401-403 in the textbook. Answer Questions 21-25 on page 404.
Read Pages 520-523 in the textbook. Answer Questions a, b, and c on page 523 Interpreting Graphs
The Mole and
Stoichiometry
4.2
Isotopes are atoms of the same element that have different numbers of neutrons. Some isotopes are radioactive,
many are not
Mass number of an individual isotope is the sum of the # of protons and the # of neutrons in an atom of that
isotope.
An element’s atomic mass, located on the Periodic Table, is a weighted average of the masses of all the known
isotopes of the element.
An element’s atomic mass represents the mass of one mole (6.02 x 1023 atoms) of the element and is called its
molar mass. Be able to determine the number of moles for a given mass of an element
Problem Set 4.1
1. Create a table that includes Element Symbol, Atomic Number, Mass Number (p + n), # Protons, #
Neutrons, # Electrons for the following elements: He, K, Mg, Sb, Au, Na, Al, Hg, Rn
2. Create a table for the following isotopes that contains the symbol –mass number form, the Mass Number Symbol
Form, # Protons, # Neutrons, # Electrons
Symbol
Mass Number
Mg
24
Mg
25
B
10
B
11
U
238
3. What is meant by the statement: “Atoms are electrically neutral?
4. Element carbon is atomic number 6. How many protons and electrons in a carbon atom?
5. What experiment led Rutherford to propose a nucleus?
6. The atomic number is 11, what is the element?
7. Imagine you were standing on the tip of a boron-11 nucleus. Describe the numbers and kinds of subatomic
particles you would see looking down on the nucleus, and those you would see looking out from the nucleus.
8. How is the atomic mass of an element calculated from isotope data?
1 mole = Molar Mass in Grams (found on the Periodic Table) = 6.02 x 10 23particles
Convert from moles to Grams: Multiply by the Molar Mass
Convert from Grams to moles: Divide by the Molar Mass
Convert from moles to particles: Multiply by 6.02 x1023
Convert from particles to moles: Divide by 6.02 x 10 23
Chemical Reactions
5.2
Show work and box answers. All answers should have units and be to the correct number of significant figures:
9. How many grams are there in 1.50 moles of Na (sodium metal)? How many atoms in the same amount?
10. How many grams are there in 0.00150 moles of H2O? How many molecules in the same amount?
11. How many moles are represented by 5.05 grams of Ne (neon gas)? How many atoms in the same amount?
12. How many moles represented by 205 grams of Ag (silver)? How many atoms in the same amount?
13. How many grams are there in 302 moles of S (sulfur)? How many atoms in the same amount?
14. (Two Steps) How many atoms are there in 89.4 grams of Fe (iron)? (Convert grams to moles and then moles
to atoms).
15. (Two Steps) How many grams is 3.01 x 1025 atoms of Copper metal (Cu)?
16. If 80% of my grades are 100, 15% of my grades are 85 and 5% of my grades are 70, what is my average?
17. If 80% of Boron atoms are B-11 and 20% of Boron atoms are B-10, what is the average atomic mass of a
sample of boron?
18. If the average atomic mass of C is 12.011, which isotope do you think is most abundant C-12, C-13 or C-14?
Explain your answer.
The chemical reaction where elements react (bond together) to form a compound is called synthesis.
Example: Hydrogen gas and oxygen gas react to synthesize water. 2H2 + O2  2H2O
The elements in a compound can only be separated by a chemical reaction. This reaction breaks the bonds
between the elements resulting in decomposition. (Example: water decomposes to form hydrogen and oxygen
gas. )
2H2O  2H2 + O2
In both reactions, the rearrangement of atoms results in chemical bonds being broken and formed.
Bond breaking requires energy while bond making releases energy
Problem Set 5.1
1. Explain in words what a reactant is and where it is found in a chemical equation:
2. Explain in words what a product is and where it is found in a chemical equation:
3. Explain in words what a synthesis reaction is:
4. Explain in words what a decomposition reaction is:
5. Identify each reaction as synthesis or decomposition. Underline the reactants. Circle the products.
a. 2H2O (g)  2H2 (g) + O2 (g)
__________________________________________
b. 2H2 (g) + O2 (g) 2 H2O(g)
c. C (s) + 2 H2(g)  CH4 (g)
d. Na (s) + Cl2(g)  NaCl (s)
e. CO (g)  C (s) + O2 (g)
Solutions
6.2
A solution is a homogeneous mixture because the separate parts of the mixture are distributed evenly and cannot
be seen. The solvent (usually water) is the part of the solution that is present in largest amount. The solute is the
substance that is dissolved in the solvent.
A saturated solution has all the dissolved solute that it can hold, and can be identified by undissolved solute
particles on the bottom after mixing. An unsaturated solution can still hold more solute.
Problem Set 6.1
Experimentation
7.2
Define and give an example of: Solvent, Solute, Saturated, Unsaturated.
Identify equipment used in the lab.
Demonstrate filtration and evaporation and explain when each can be used to physically separate a mixture.
Define filtrate as the liquid that passes through the filter.
Measure volume of a liquid in milliliters (mL) using a graduated cylinder and stating measured digits plus the
estimated digit. Be sure to read the bottom of the meniscus of the liquid.
Measure mass in grams (g) using an electronic balance and identifying the estimated digit.
Be able to construct a data table for both discrete and continuous data.
A bar graph can be used for both discrete and continuous data, while a line graph should only be used
continuous data.
A special kind of bar graph is called a frequency distribution.
In all types of graphs, the x axis is usually the independent variable and the y axis is the dependent variable
Problem Set 7.1
1. Give the Correct number of Sig Figs for each of the following numbers.
Number
Number
Number
200.0
2.0 x 102
10000.10
0.0001
2.001 x 102
12342.98
303
6.02 x 1023
5
303.00
100,001
5.00
0.0012
105.0003
0.001201
0.001200
20.00001
1000
2) 357.89 + 0.002 =
3) 17.95 + 32.42 + 51 =
4) 5.5 + 3.7 + 2.97 =
5) 84.675 - 3 =
6) 75 - 2.55 =
7) 10 - 9.9 =
8) 18.221 +11 =
9) 22.21+ .009=
10) 0.0078 + 0.12 =
11)50.00 x 2.50000 =
12) 2.3 x 3.45 x 7.42 =
13) 1.5007 x 0.009 =
14) 51 / 7.02 =
15) 208 / 9.0122 =
16) 0.003675 / 5.0 =
17) 55.0/ 11.0
18) 123.56 x 4 =
19) 122 x 0.001
20) 303 x 2.001
21) 56.88/ 8.888
22) 101 x 0.15 =
Lab Equipment and Safety- this will go into your lab notebook.
Identify the following equipment in the lab and draw the item:
Beaker
Wire Gauze
Test Tube Rack
Watch Glass
Erlenmeyer Flask
Clay Triangle
Crucible with lid
Graduated cylinder
Wash bottle
Test Tube
Evaporating Dish
Mortar and Pestle
Ring Stand
Stiring Rod
Buret
Spatula
Funnel
Balance
Identity the piece of equipment that would be best to use for the following:
1.
Crushing a large solid crystal into a powder _____________________________
2.
Massing a piece of filter paper________________________________________
3.
Measuring 15.0 ml of a liquid sample__________________________________
4.
Dispensing 5.5 ml of a liquid sample __________________________________
5.
Heating a substance in a contained vessel ______________________________
6.
Estimating 200 ml of a liquid sample__________________________________
7.
Holding filter paper during filtration___________________________________
8.
Rinsing out a beaker during a lab______________________________________