The Periodic Table
Elements are arranged and identified on
the periodic table by the number of
protons they have in their nucleus.
The ATOMIC NUMBER is equal to the
number of protons in an element.
While the total number of electrons is
important, it is even more important that
you understand how many valence electrons
an atom has.
What are valence electrons?
Valence electrons are the electrons in the
outer energy level.
How many valence electrons do each of
the following atoms have?
1 valence
electron
2 valence
electrons
3 valence
electrons
Elements in the same column
or group have similar physical
and chemical properties.
This because they all have the
same number of valence
electrons!
Reading Roman
numerals:
I=1
II = 2
III = 3
IV = 4
V=5
VI = 6
VII = 7
VIII = 8
How many
valence
electrons do
the elements of
group 2 have?
II = 2
You will ignore
the A’s and B’s.
How many
valence
electrons do
the elements of
group 17 have?
VII = 7
How many
valence
electrons do
the elements of
group 14 have?
IV = 4
Remember: We can determine the number of valence
electrons in the atom of an element by using the
Roman numerals on the periodic table.
How many
valence
electrons do
the elements
of group 16
have?
VI = 6
How many
valence
electrons does
phosphorous
have?
V=5
Lewis Dot Diagrams:
Lewis dot structures show the number of valence electrons in
an atom using an atoms symbol surrounded by dots
representing the valence electrons. Use the Roman numerals
on your periodic table to determine the number of valence
electrons for elements below. Decide which Lewis dot diagram
is an accurate representation.
Which Lewis Dot Diagram below accurately
represents hydrogen?
H
H
H
Which Lewis Dot Diagram below accurately
represents nitrogen?
N
N
N
Which Lewis Dot Diagram below accurately
represents carbon?
C
C
C
Which Lewis Dot Diagram below accurately
represents boron?
B
B
B
Which Lewis Dot Diagram below accurately
represents phosphorous?
P
P
P
There are several things you will need to
memorize about the periodic table.
Find the dark jagged line on
the Periodic Table
On the left side of this
line are all of the metals
On the right
side of this line
are all of the
nonmetals
Chemical reactions occur when
atoms gain, lose, or share electrons.
Metals ________________
lose or donate electrons.
+ charge.
This always gives them a ____
gain
Nonmetals _________
electrons.
This always gives them a ____ charge.
_
Nonmetal can also share electrons with one
another, and this is what makes a covalent
compound.
gains 1 electrons
Does NOT gain or lose
gains 2 electrons
donate 1 electron
donate 2 electron
You need to understand the pattern of elements
gaining and losing electrons on the periodic table.
Think about counting from the outside to the inside!
Metals lose or donate electrons and
nonmetals gain electrons
Because of this
metals react with nonmetals!
+1
sodium
sodium chloride
chlorine
-1
We can see that it is a 1:1 ratio between sodium and
chlorine, but why does it work out that way?
Once again, it has to do with the
valence electrons!
+1
-1
sodium
sodium chloride
chlorine
Since sodium donates 1 electron and chlorine gains 1
electron, they join together in a 1:1 ratio.
This is true for all of the combinations of
Group 1 and Group 17 elements!
HCl
LiF
NaBr
KF
CsI
RbCl
HBr
KCl
LiF
RbBr
KBr
NaI
LiCl
FrCl
HF
They are all 1:1 ratios!
This is also true between metals that lose
2 valence electrons and the nonmetals
that gain 2 valence electrons.
+2
-2
magnesium
magnesium sulfide
sulfide
Since magnesium donates 2 electrons and sulfur gains
2 electrons, they join together in a 1:1 ratio.
This is true for all of the combinations of
Group 2 and Group 16 elements!
BeO
MgS
SrO
BaSe
CaTe
CaS
BeSe
MgO
SrS
BaO
MgSe
CaO
BeS
BaTe
SrSe
They are all 1:1 ratios!
The Periodic Table can be used to determine
the charge of all of the principal elements!
+1
+2
+3
+4
or
-4
0
-3 -2 -1
The elements that lay on either side of the
dark, jagged have rather unique properties.
Sometimes they act like metals, and
sometimes they act like nonmetals.
Because of this, they are called
Metalloids
The metals in the middle of the periodic table
are known as the transition metals.
Transition Metals
Group 1 = Alkali Metals
Group 2 = Alkaline Earth Metals
Group 17 = Halogens
Group 18 = Noble Gases
Halogens
Noble Gases
Alkali Metals
Alkaline Earth Metals
There are several groups on the periodic table
whose name you should have memorized.
You also need to know that Iron, Cobalt, and Nickel
have special properties such as the ability to be made
into magnets. Together, these three elements are
known as the Iron Triad .
Iron Triad
Which group on the periodic table
undergoes the fewest chemical
reactions?
Group 18
The Noble Gases
They are inert gases. This is a chemical
property that means they will not react
with other substances.
Inert means inactive!
Ionic compounds are ALWAYS
between a metal and a nonmetal.
On the left side of this
line are all of the metals
On the right
side of this line
are all of the
nonmetals
Covalent compounds are ALWAYS
between nonmetals.
On the right
side of this line
are all of the
nonmetals
Understanding the previous facts at a conceptual
level is critical to your success in chemistry. Using
this knowledge, determine the identity of each of
the following unknown elements.
XCl3
The formula above shows the ratio of an unidentified
element, X, to chlorine in a covalent molecule. Which
element below is most likely the identity of Element X?
A sodium
B neon
C phosphorous
D copper
Since it is a covalent molecule, it has to be a nonmetal. It
cannot be neon since neon is an inert noble gas that would
not react with chlorine.
NaX
The formula above shows the ratio of an unidentified element,
X, to sodium in an ionic salt. In which group on the periodic
table does Element X most likely belong?
A Group 1
B Group 2
C Group 17
D Group 18
Since it is an ionic salt, it has to be a nonmetal since
sodium is a metal. It cannot be group 18 since group 18 is
the inert noble gases that would not react with sodium.
XF
The formula above shows the ratio of an unidentified element,
X, to fluorine in an ionic salt. Which group below is most likely
the identity of Element X?
A sulfur
B lithium
C arsenic
D krypton
Since it is an ionic salt, it has to be a metal since fluorine is
a nonmetal.
The Law of Conservation of Mass
According to the Law of Conservation of Mass, the
mass of the reactants should equal the mass of the
products.
Reactant 1 + Reactant 2
Product
Which scientist’s results below best support the
Law of Conservation of Mass?
Mass of
Mass of
Mass of
Scientist
Reactant 1
Reactant 2
Product
Scientist A
19 g
22 g
42 g
Scientist B
19.4 g
22.4 g
41.7 g
Scientist C
19.36 g
22.37 g
41.74 g
Scientist D
19.364 g
22.372 g
41.736 g
Solving for Mass
When this concept is shown with a chemical equation,
nothing changes about how it should be solved.
Hydrogen + Oxygen
Water
16.0 g
128 g
?g
16.0 grams of hydrogen reacts with 128
grams of oxygen. Assuming all of the reactants
are used up, how much water will be produced?
16.0 g + 128 g = 144 g