Name:________________________________Period:___________________________Date_______________________
Unit 2 review
1. Look at the models of the atom that have progressed over time, which scientist.
Thought it looked like a solid ball? Dalton
Thought it was a positive background with negative particles stuck in it? Thomson
Discovered the nucleus and thought the atom was mostly empty space? Rutherford
Determined that electrons are arranged in specific energy fields? Bohr
Discovered the neutron? Chadwick
What does the current model of the atom look like? The cloud model
2. What are the 3 particles an atom is made of? What is the electric charge of each?
Proton
Neutron
Electron
positive
neutral
negative
3. Look at the periodic table.
a. For the element oxygen (O) find the: # of protons # of neutrons and # electrons for an electrically neutral
atom.
# protons 8
# neutrons 8
# electrons 8
b. Draw the Bohr diagram for oxygen (if you don’t remember what a Bohr diagram is. Look back at the first
question) (remember 2-8-8)
c.
d. If you added a neutron to this atom what would it be called? An oxygen isotope
e. How would you make your model an oxygen ion? By gaining 2 electrons
f.
Is an oxygen ion positive or negative? Why? An oxygen atom will gain 2 electrons to fill its outer
most ring. Atoms want full outer shells to be stable. When oxygen gains 2 electrons the overall
charge of the atom is now negative because it has more (10) electrons than (8) protons. An
oxygen ion would have a negative charge.
g. Could the atom have 9 protons and still be oxygen? Explain why or why not. No because at atom with
9 protons is fluorine. The # of protons defines what type of element the atom is.
4. Look at the periodic table again.
a. What are the all elements on the left of the zig zag line? metals
b. What are the elements on the right? Non-metals
c. What are the elements that touch the line? Metalloids
What are the general properties of metals?
Luster
Conduct electricity and heat
Ductile
Malleable
Lose 1-3 valence electrons
What are the general properties of non-metals?
Dull
Brittle
Poor conductors of electricity and heat
Gain 1-3 valence electrons
What type of bonds are formed between metals and non-metals? Ionic bonds
What type of bonds are formed between non-metals and non-metals? Covalent bonds
When sodium bonds ionically with chlorine 1 electron is transferred. Explain why. Sodium will lose 1 electron to
become stable (have a full outer shell). Chlorine needs 1 electron to become stable (have a full outer shell)
What is an element? The simplest, purest substance that is made up of only 1 kind of atom.
What is a compound? 2 or more elements chemically bonded together
What is a mixture? 2 or more substance put together that are not chemically bonded together.
Which of the above can you separate by physical means? (filtering, using your hands, using magnet, etc…)
A mixture because the substances are not chemically bonded to one another.
What is a solution? A homogenous mixture. A mixture where you cannot see the individual parts that make it
up.
What is a saturated solution? A solution that cannot hold anymore solute.
What is an unsaturated solution? A solution that can hold more solute.
Name the physical properties of substances.
Mass
Density
Length
Volume
Color
Conductivity
Malleability
Luster
Name the chemical properties of substances.
Flammability
Reactivity to water, air, acids/bases
Tendency to corrode
Water freezing is what type of change? Physical or chemical? Why? Physical because the chemical makeup of the
substance never changes. The process of H2O going from liquid to solid to gas never changes it chemically.
Paper burning is what type of change? Physical or chemical Why? A chemical reaction because the paper is
chemically different after being burned. The result is a different substance with different properties than the
paper.
What does a chemical change result in? A chemical reaction which forms a new substance with new properties
What does the law of conservation of mass say? During a chemical reaction atoms are never created or destroyed.
What are the 3 states of matter? Solid
Liquid
Gas
In which do the molecules move the fastest? Gas
What is the fourth state of matter? Plasma
What are the 6 phase changes? List what state is changing to what for each.






Melting
Freezing
Vaporization
Condensation
Sublimination
Deposition
solid to liquid
liquid to solid
liquid to gas
gas to liquid
solid to gas (dry ice)
gas to solid (frost)
What do the flat points on a phase change diagram indicate? A phase change, heat (thermal energy) is speeding up
the molecules of water causing the water to change from solid to liquid to gas
What is the freezing point of water in (®C)? 0
What is the boiling point (®C)? 100
What does density measure? The amount of mass in a given volume
What is the formula for density? Mass divided by volume
Look at the table:
Liquid
A
B
C
D
E
Density (g/ml)
1.04
0.93
0.67
1.43
0.87
If you poured these liquids in a container how would they stack from bottom to top? Why?
Top
C least dense
E
B
A
Bottom
D
most dense