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.
Quick ReviewQuick Review
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
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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 = 1II = 2III = 3IV = 4V = 5VI = 6VII = 7VIII = 8
How many valence electrons do the elements of group 2 have?
II = 2You 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
How many valence electrons do the elements of group 16 have?
VI = 6
How many valence electrons does phosphorous have?
V = 5
Remember: We can determine the number of valence electrons in the atom of an element by using the Roman numerals on the periodic table.
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 NWhich Lewis Dot Diagram below accurately
represents carbon?
C C C
Which Lewis Dot Diagram below accurately represents boron?
B B BWhich 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 ________________ electrons.This always gives them a ____ charge.
lose or donate+
Nonmetals _________ electrons.This always gives them a ____ charge.
gain _
Nonmetal can also share electrons with one another, and this is what makes a covalent
compound.
You need to understand the pattern of elements gaining and losing electrons on the periodic table.
dona
te 1
ele
ctro
ndo
nate
2 e
lect
ron
gain
s 1
elec
tron
sD
oes
NO
T ga
in o
r los
e
gain
s 2
elec
tron
s
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!
sodium chlorinesodium chloride
+1 -1
sodium chlorinesodium chloride
+1 -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!
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!
HClLiFNaBrKFCsI
RbClHBrKClLiFRbBr
KBrNaILiClFrClHF
They are all 1:1 ratios!
magnesium sulfidemagnesium sulfide
+2 -2
This is also true between metals that lose 2 valence electrons and the nonmetals
that gain 2 valence electrons.
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!
BeOMgSSrOBaSeCaTe
CaSBeSeMgOSrSBaO
MgSeCaOBeSBaTeSrSe
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+4or-4 -3 -2 -1
0
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
There are several groups on the periodic table whose name you should have memorized.
Alka
li M
etal
sAl
kalin
e E
arth
Met
als
Hal
ogen
sN
oble
Gas
es
Group 1 = Alkali MetalsGroup 2 = Alkaline Earth MetalsGroup 17 = HalogensGroup 18 = Noble Gases
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 18The 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.
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
XCl3
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.
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
NaX
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.
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
XF
Since it is an ionic salt, it has to be a metal since fluorine is a nonmetal.
The Law of Conservation of Mass
Scientist Mass of Reactant 1
Mass of Reactant 2
Mass of 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
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?
Hydrogen + Oxygen Water16.0 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?
Solving for MassWhen this concept is shown with a chemical equation,
nothing changes about how it should be solved.
16.0 g + 128 g = 144 g
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