Transcript Final Review Answer Key

Chemistry Unit Review
Answer Key
Structure of an atom
Electron
Negative
Proton
Neutron
Positive
Neutral
»
2. What element is this atom? How can you tell by looking at the
diagram? Lithium; The element has 3 protons which is the same
as the atomic number on the periodic table.
Structure of an atom con’t.
3. What is the mass of this atom? 7
How can you tell by looking at the diagram? The
mass of an atom is found by adding the protons
and neutrons together. This atom has 3 protons +
4 neutrons.
4. Which subatomic particle has the smallest mass?
electron
5. What happens to this atom when you…
a. Remove an electron? It becomes an ion(cation)
b. Remove a neutron? It has less mass and is
called an isotope
c. Add a proton? It becomes Berylium
6. How could you change this atom into helium? You
would have to remove 1 proton
Periodic table trends and organization
1. Why are He, Ar, and Kr all un-reactive with other
elements? Their outer shells are either full or have 8
electrons making them very stable
2. Give a list of three elements you expect to have
similar chemical properties, and explain why. Could
be any 3 elements in a group(column); all have the
same number of valence electrons giving them
similar properties
3. What are valence electrons? The outermost shell of
electrons; can be 1 to 8 of them
4. How do valence electrons determine the chemical
properties of an element? Explain why using at least
two examples. Valence electrons are what
determines the reactivity of an atom as well as what
type of bond it is most likely to form. Ex: Sodium has one
valence e-, so it is very likely to react to get rid of this electron. Neon has 8
so it is very stable.
Periodic table trends and organization con’t.
5. Fill out the following table.
Element
Group
#
Period
#
Atomic
#
Atomic
Mass
# of
Protons
# of
Neutrons
# of
Electrons
# Valence
Electrons
#
Energy
Shells
Be
2A 2
4
9.012
4
5
4
2
2
Cl
17
3
17
35.45
17
18
17
7
3
Kr
18
4
36
83.79
8
36
48
36
8
4
6. Categorize these elements as either metals or non-metals.
Carbon Sodium Calcium Silver Hydrogen Iron Oxygen Fluorine
Metals
Sodium, Calcium, Silver, Iron
Non-metals
Carbon, Hydrogen, Oxygen,
Fluorine
Ions and isotopes
1.Fill out the table below for isotopes of carbon.
Isotope
# of
Protons
# of
Neutrons
# of
Atomic
Electrons Mass
Carbon-12
6
6
6
12
Carbon-13
6
7
6
13
Carbon-14
6
8
6
14
2. How do you change the charge of an atom? By adding or
taking away electrons from the outer shell.
Chemical bonds
1. Identify the following substances as either an element or a
compound.
Substance
NaOH
Element or
Compound?
Compound
CO
Compound
Co
Element
CuSO4
Compound
Cu
Element
2. How many elements are in a molecule of CaSO4? How many
atoms total? 3 Elements and 6 total atoms
Chemical bonds con’t
3. What is the chemical formula for this molecule? How do
you know?
NO2 ; There are 2 atoms of oxygen
and 1 atom of nitrogen. The
nitrogen comes first because it is
in the group before oxygen.
4. Why do different atoms bond together to make compounds?
Atoms bond together to satisfy the full outer shell or 8 valence
electron rule which makes them more stable.
5. Describe what happens to valence electrons in ionic bonding.
In an ionic bond one atom gives up valence electrons making
it a positive cation while the other takes in those valence
electrons making it a negative anion.
6. Why do negatively charged and positively charged ions
combine to form compounds? The opposite charged
atoms are attracted to each other and they form a weak bond.
Chemical bonds con’t
7. Write the chemical formula for the following compounds. Also,
write the ions and their charges for each compound.
Name
Positive charged Ion
(include the chemical
symbol and charge)
Negative charged Ion Chemical
(Include the chemical
Formula
symbol and charge)
Ex: Magnesium
Iodide
Mg+2
2 I-1
MgI2
Potassium Bromide
K+1
Br-1
KBr
Calcium Chloride
Ca+2
Cl-1
CaCl2
Magnesium Oxide
Mg+2
O-2
MgO
8. Describe what happens to valence electrons in covalent
bonding. Valence electrons are shared by each atom in a
covalent bond.
Chemical bonds con’t
9. Write the formula for a covalent bond between
carbon and Chlorine.
CCl4
10. Classify the bonding in each compound as
covalent or ionic.
Carbon dioxide (CO2)
Aluminum sulfide (Al2S3)
Silicon dioxide (SiO2)
Potassium bromide (KBr)
Sodium chloride (NaCl)
Magnesium oxide (MgO)
covalent
ionic
covalent
ionic
ionic
ionic