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Chemistry Review
The basic unit of matter is the atom. The atom
is made up of even smaller particles. Three of
these subatomic particles are the proton, the
neutron, and the elcetron. Both the positively
charged protons and the electrically neutral
neutrons form the nucleus of the atom. The
negatively charged electrons travel around the
nucleus of the atom in a series of distinct
energy levels.
The number of protons in the nucleus of
an atom, or the atomic number, Is used to
Identify the atom. The total number of protons
and neutrons in the nucleus is calla the mass
number.
Substances that consist entriely of one
type of atom are called elements. Each
element Is represented by a chemical symbol.
The number of protons in an atom of an
element never changes. The number of
neutrons however, may vary from one atom of
an element to the next. Atoms of the same
element that have different numbers of
neutrons are called isotopes. Certain kinds of
isotopes are radioactive.
Substances that consist of more than
one type of atom are called chemical
compounds. Most of the materials in the living
world are compounds.
Match the numbered terms with their definitions. Write the letter of the definition that
corresponds with each term In the space provided.
0
1. mass number
2. chemical symbol
3,
....
isotopes
4. atomic number
. ....... S. nucleus
6. neutron
..
,Morns of the same clement with difierent numbers
of neutrons
_,f
posftivelychargad particle
nr—subatomic particle located outside the nucleus of
the atom
substance that contains two or more difierent
kinds of atoms.
/climber of protons in an atom
torthand way of representing an element
, ..frar
7. element
Ate-Center of the atom
8. proton
Ai/electrically neutral subatomic particle
O. chemical compound .umber of protons plus the number of neutrons in
an atom
C10. electron
J.--substance consisting of only one type
of
atom
11. In the space below, draw and label the following parts of an atom: electron, neutron, proton,
nucleus and energy level.
Counting Atoms
The formula for a compound indicates the elements that make up the compound and the
number of atoms of each element present in the compound. These numbers of atoms are
indicated by the use of small numbers called subscripts. Sometimes groups of atoms act as a
single atom. Such a group of atoms is called a radical. if a radical Is used In a formula more
than once, the radical is put in parentheses and the subscdpt appears outside the parentheses.
When a subscript appears outside the parentheses, It indicates that all the demerits inside
parentheses should be multiplied by that StIbratiptFOr example, the formula Fe(010 3 indicates
the combination of one atom of iron, Fe, three atoms of oxygen, 0, and three atoms of
hydrogen, H.
In the following examples, list each element In the compound and the number of atoms of
each element present. The first example has been done for you. You may already be familiar
with some of the compounds.
Atoms In Formula
Formula
list
Name
Ca = calcium 1
CaCO1
Calcium carbonate
Limestone
Aspirin
Pain reliever
Magnesium
hydroxide
Found In milk of'
magnesia
Paradichlorobenzene
Moth crystals
C
e_
Trinitrotomene CST)
.
C4140003
Explosive
•
I
tii
14°1.
Atoms that have the same number of protons and electrons are elect ically neutral. However, atoms
may gain or lose electrons during chemical reactions. This creates an imbalance of negative and
positive charges. Atoms may have a negative charge because they have gained extra electrons.
Such atoms are called negative ions. Other atoms may have a positive charge because they have
lost electrons. These atoms are called positive ions.
The following table contains information about several atoms. Using what you have learned In
the preceding paragraph, complete the table. Enough information has bean provided for you
to fill In all the blanks.
Mass ft = it of protons + # of neat ons
Atomic # = # of protons
eiemem
Aluminum (AI)
Atomic
Number
Mass
Number
18
27
Bromine (Bd
SC
Calton (0)
8
Carbon (t)
6
i4
Helium (He)
2
4
Number of Number ot Number of
Protons
(2)
35
li.
.0
Neutrons
Elections
l tic
is
45
36
6
ti
a
Isotope,
fort, or
Neutral Mont
{
neutral atom
The following diagram shows a small portion of the periodic table of the elements. Use the
information in the diagram to answer questions 1 through 9.
He
4
a
ibeon
Carbon
13
14
12
Na Mg
wathg„„
—iY1155
Si
AU
:mob mapnoeboni
Alurninuirr,
Ne
0
°Mos
nhotphnms
Wren
hi
Sr
at
ap
Fluorine
t3
a.
17
is
CI
Ar
Chlorine
ATM
oo
35
1. What is the boldfaced letter or letters in the center of the box? tik\L2. What
is the number above the boldfaced letter or letters? '&$
lJ
AVa
4-( - 'r$`-L '?
3. Whthir it. the nuber below the name of the element?
Use the periodic table above to till out the following table.
Verner?:
Number of Number of
Neutrons
incises
In Atom
In Atom
ol Number of Number ol
Electrons Electrons Electrons
in Second
in First
in Atom
Number
Energy
Level
Energy
Level
Number of
Electrons
in Third
Energy
Level
4..
Carbon
'
Li
e
aicrine
.., .
Heiman
liydir og en
C
t
,..—
)
1.ilhiu m
- )
/..-
-1
..
Chemical Bonding
Use the following terms to label the structures shown in the diagram below: electron,
nucleus, neutral atom, positive ion, negative ion, ionic bond.
Af
p
Chlorin° (CU
(*mote aloe,
1. What basic process is shown in the previous diagram?
2. How many electrons can the innermost energy level hold?
3. What kind of bond is shown? Explain.
The outermost?
c
4. How does an ion differ from a neu ral atom?
Use the following terms to label the structures shown in the diagram below: electron, shared
electron, molecule.
fl
1
9 dr
a 9
a 0 r
d,
•
Oxy 'en (Oa)
i,stat0
-
v
5. What kind of bond is shown in the diagram? Explain.
6. What do the dots in the above diagram represent?
7. What is the above diagram called?
e
el
-N-Y`
C)
) `-‘
Chemical Reactions
Any process in which a chemical change occurs is known as a chemical reaction. As you learned in
this section, a chemical reaction converts elements or compounds known as reactatnts into elements
or compounds known as products. A chemical equation uses symbols'and formulas to descrive a
chemical reaction.
In the chemical reactions described below, identify the reactant(s) and the product(s). Then '
write a balanced equation for each reaction.
1. A sodium ion (Na) eacts with a chlorine ion (CO to form the compound sodium chloride (NaCI).
Reactant(s):
b,c)("*""
C, —
Equation:
IC* 13?
aik
Product(s):
7
iC-50-
\-)c- e-1
2. Magnesium oxide (MgO) is produced when a magnesium ion (Mg &) reacts with an oxygen ion
(02).
it+
4Reactant(s): ‘Ner
Product(s):
Equation:
t‘s..1V. C
Name
BALANCING EQUATIONS
Balance the following chemical equations.
2_ N20
2. jkl2 +
—>
3.
---> 3NH3
4.
CH4 +2_02
-4
CO2 +2H20
-->
5... KI + 01 2 jKCI
+ 12
672,, S
+3 02
7_303
H 2O
7. 2,..H202
8. -2. Na
+111 20
9,-2,H20
KCIO3
11. K3 PO4
-->
+ 0,
-2,NaOH
+
---> 2,1 2 + 02
---> -7 KCI 302
HCI
A2. CO 2 + H2O
--->
3 KCI + H3PO4
H2003
13.
K20 + H 2O
_KOH
14.
Mg +7 HCI
MgCl2 +
19 KOH + H2SO4
Biology IF8765
H2
K2SO4
H2O
14
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