Study Guide for PS-B #1
KEY
Name:____________________________________________________________________ per_____
Be able to define:
 Ion- a charged particle made when an atom loses or gains electrons to get a full outer shell
 Isotope- atoms with different atomic masses because they have a different number of neutrons
 Hydrophobic-water-fearing
 Hydrophilic- water- loving
 Covalent Bond- bond between two nonmetals in which electrons are shared
 Ionic Bond- bond btwn a metal and a non in which electrons are transferred and ions are made
 Metallic Bond- bond btwn two metals
 Conductivity- ability to conduct electricity (to move electrons through it)
 Polar – has a partial positive and a partial negative end to the molecule
 Nonpolar- has no partial charges- a completely neutral molecule
1. Now that you understand more about atoms and elements...describe what a chemical change is? Explain
an example of a chemical change. A chemical change occurs when bonds are broken or formed and new
molecules are created. Flammability is a chemical PROPERTY because when something burns, it reacts
with oxygen and forms new compounds. So burning something would be a chemical CHANGE.
2.
An atom has 8 protons and 10 electrons. Write the chemical symbol for this ion. Be sure to indicate the
proper charge.
O23. Why are Lewis Dot structures more useful than Bohr models when predicting bonding?
Lewis dot structures help us focus on the VALENCE electron. Since these are the electrons are the ones
involved in bonding, it helps us predict if they will form ions and how they will react with other atoms.
Bohr models are misleading because they do not show the actual valence shell.
4. Predict the ion that will form for each of the following. Draw the lewis dot structure to help you.
a. Fluorine
F1-
b.Oxygen
O2-
c. Magnesium
Mg+2
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5. How many atoms of each element are present in the following molecules?
a. H2O
2 Hydrogen, 1 Oxygen
b. CaCl2 1 Calcium, 2 Chlorine
c. C6H12O6
6.
6 Carbon, 12 Hydrogen, 6 Oxygen
Circle the correct words to complete the sentences.
a. A cation is formed when an atom (loses/gains) electrons to have a (positive/negative) charge.
b. When an atom gains electrons, it gets more (positive/negative).
c. When an atoms gains electrons, it becomes an (ion/isotope).
7. What is wrong with each of the following electron dot diagrams?
:Li.
Lithium only has ONE valence electron (Lewis Dots do NOT show ALL the electrons, just the
outer shell)
: C:
Electrons must be placed on all four sides before you put any together on one side.
..
: P:
Phosphorus only has 5 valence electrons, AND they are not on all four sides.
8. State the octet rule. Why does it not apply to Helium?
Atoms want to have 8 valence electrons (8 electrons in their outer shell)
because most atoms will have a full outer shell with 8.
The octet rule works for most atoms
Helium only fills the first shell and 2 electrons makes it “full”…so He only needs 2 electrons to be nonreactive.
9. How many protons, neutrons and electrons are in the following:
a. C-14
p=__6___
n=___8___ e=__6____
b. C-12
p=__6___
n=___6____ e=___6___
c. O 2-
p=__8___
n=___?____ e=___10___
10. What is the “rule of thumb” when determining if atoms will form an ionic or covalent bond?
Metal with a Metal metallic
Metal with a NONmetal ionic
NONmetal with a NONmetal covalent
Two of the SAME nonmetal nonpolar covalent
Two different nonmetals polar covalent
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11. Explain the phrase “like dissolves like.” Be sure to discuss polar vs nonpolar and hydrophobic vs.
hydrophilic.
Polar molecules can dissolve in polar solvents like water, but nonpolar molecules will not. They can only
be dissolved in nonpolar solvents like oil. This is why we call polar molecules HYDROPHILIC because
they are “water-loving” and nonpolar molecules HYDROPHOBIC because they are “water fearing”
12. Explain why water is said to be polar.
13. Draw two water molecules. Show how they would interact with each other. How would they arrange
themselves? Label the following bonds: hydrogen bond, polar covalent bond.
Water molecules arrange themselves to keep the oxygens as far away from each other as possible, while keeping
the Hydrons near the Oxygens. (The Oxygen’s are attracted to the Hydrogens)
Polar
Covalent
Bond
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14. What kind of bond will form for each of the following compounds:
Molecule
Metals/Nonmetals
Electronegativity diff
Type of bond
(ionic, metallic, nonpolar covalent, or
polar covalent)
HCl
Non/Non
2.1-4=1.9
Polar covalent
Cu2
Metal/Metal
1.9-1.9=0
Metallic
MgO
Metal/Non
1.2-3.5=2.3
Ionic
NO2
Non/Non
3-4=1
Polar covalent
H2O
Non/Non
2.1-3.5=1.4
Polar covalent
CaCl2
Metal/Non
1-3=2
Ionic
NaCl
Metal/Non
.9-3=2.1
Ionic
O2
Non/Non
3.5-3.5=0
Nonpolar covalent
Remember…
Electronegativity difference of:
Greater than 1.7= ionic
Between .4 and 1.6= polar covalent
0-0.3= nonpolar covalent
15. What makes metals good conductors?
The electrons are free to move between the metal ions.
(recall that electricity is the movement of electrons)
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