1. 3 Elements and Compounds
This reclining Buddha in Thailand is made of gold.
Foundations of College Chemistry, 14th Ed.
Morris Hein and Susan Arena
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

2. © 2014 John Wiley & Sons, Inc. All rights reserved.
Chapter Outline
3.1 Elements
A. Distribution of Elements
B. Names of the Elements
C. Symbols of the Elements
3.2 Introduction to the Periodic Table
A. Natural States of the Elements
B. Diatomic Elements
Compounds and Formulas
A. Molecular and Ionic Compounds
B. Writing Formulas of Compounds
C. Composition of Compounds
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3. Elements and Atoms
An element is a fundamental substance that cannot be
broken down by chemical means into a simpler substance.
Elements are the building blocks of matter.
Elements can occur naturally or be synthesized in labs.
The smallest unit of an element that retains its
properties and chemical behavior is called an atom.
Atoms are made up of subatomic particles,
but they do not have the properties of the element.
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4. Elements Currently, 118 elements are known.
88 of these elements are naturally occurring.
At room temperature,
only bromine (Br) and mercury (Hg) are liquids.
At room temperature, 11 elements are gases:
hydrogen (H2), nitrogen (N2), oxygen (O2),
fluorine (F2), chlorine (Cl2), helium (He),
neon (Ne), argon (Ar), krypton (Kr),
xenon (Xe) and radon (Rn).
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5. Elements Ten elements make up almost 99 % of the mass of the
Earth’s crust, seawater and atmosphere.
Oxygen accounts for about 20 % of the atmosphere and
is found in nearly all rocks, sand and soil.
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6. Elements The most prevalent elements in the human body
are oxygen (65 %), carbon (18 %) and hydrogen (10 %).
Some elements in the body are present in tiny amounts,
like chromium and copper, but are crucial for life.
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7. Names of Elements Many element names are derived from Greek, Latin or
German words that describe a property of the element.
Iodine comes from the Greek word iodes meaning
“violetlike” and iodine is violet colored as a vapor.
Some elements are named for the location of
their discovery, such as germanium which was
discovered in 1886 by a German chemist.
Other elements commemorate famous scientists,
like curium which is named after Marie Curie.
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8. Symbols of the Elements
Each element has an abbreviation called a symbol.
Fourteen elements have single letter symbols
and the rest have two letter symbols.
iodine (I) barium (Ba)
What element has the following symbol?
nitrogen
gold
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9. Symbols of the Elements
The table below contains symbols
for the most common elements.
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10. Symbols of the Elements
The table below contains symbols
of elements derived from early names.
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11. Symbols of the Elements
The first letter of a symbol must always be capitalized.
If a second letter is needed, it should be lowercase.
Consider the element cobalt:
Cobalt has the symbol Co
Writing CO would symbolize elements C (carbon) and
O (oxygen) and would represent carbon monoxide.
In order to succeed in chemistry, you should work to learn
many of the elements on the periodic table.
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12. Introduction to the Periodic Table
The Periodic Table was designed by Dimitri Mendeleev
in 1869 to organize elements based on their properties.
Elements with similar chemical properties are placed
in columns called groups.
Four groups have special identifying names,
like Noble Gases, which are all unreactive gases.
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13. Introduction to the Periodic Table
The eight tall columns are called representative elements,
or main group elements. These are shown in red.
The elements in the center are called the transition metals. These are shown in purple.
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14. Introduction to the Periodic Table
Elements can be further classified as metals,
metalloids and nonmetals.
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15. Metals Metals are: solids at room temperature (except mercury) shiny
good conductors of heat and electricity
malleable (can be shaped)
ductile (can be drawn into wires)
Most metals have a high melting point and density.
Common metals include aluminum, gold, platinum,
silver, tin and iron.
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16. Metals
Metals readily combine with nonmetals to form compounds but rarely combine with other metals.
Some metals are found in their free states,
like copper, gold and silver.
Some metals are mixed to form homogeneous mixtures
called alloys, like brass, bronze, steel and coinage metals.
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17. Nonmetals Nonmetals: are not shiny
have fairly low melting points and densities
are poor conductors of heat and electricity
Nonmetals combine with each other to form molecular
compounds and with metals to form ionic compounds.
Common nonmetals found naturally include carbon,
nitrogen, oxygen and sulfur.
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18. Metalloids Metalloids have properties between metals and nonmetals.
These elements are positioned diagonally on the
Periodic Table separating the metals and nonmetals.
Certain metalloids, like boron, silicon and germanium
are the materials used in electronic devices.
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19. Let’s Practice! What is the symbol for silver? S Si sulfur Ag AuSr
sulfur
silicon
silver
gold
strontium
Which of the following elements are metals?
Na, Mo, Cl, S, Mg, Pt, Kr, I, C, Cu
Na, Mo, Mg, Pt, Cu
Metals are typically found on the left of the Periodic Table.
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20. Natural States of the Elements
Elements tend to be reactive and combine with other
elements to form compounds.
It is rare to find elements in nature in their pure forms.
Gold, silver and platinum (the noble metals) have
low reactivity and are found uncombined in nature.
Air is composed mainly of nitrogen and oxygen,
a homogeneous mixture of diatomic elements.
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21. Diatomic Elements Seven elements exist as diatomic molecules.
These molecules contain exactly two atoms.
Diatomic elements can be separated.
In water (H2O), neither hydrogen or oxygen is diatomic.
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22. Compounds and Formulas
A compound is a substance containing two or more
elements that are chemically combined in a
definite proportion by mass.
Compounds, unlike elements, can be decomposed
chemically into simpler substances.
Elements in compounds are always combined
in whole number ratios.
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23. Molecular and Ionic Compounds
Compounds fall into two general types,
molecular and ionic.
Molecular compounds are held together by covalent bonds
and ionic compounds are held together by attractive
forces between the positive and negative charges.
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24. Molecules and Ions
Molecules are the smallest unchanged individual unit
of a compound formed by two or more atoms.
A molecule cannot be further divided
without destroying its identity.
Ions are charged atoms or groups of atoms.
Ions can be positively or negatively charged.
A positively charged ion is called a cation.
A negatively charged ion is called an anion.
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25. Compounds More than 50 million compounds are currently known.
Each compound has a unique set of properties.
Consider water (H2O) and hydrogen peroxide (H2O2).
Property
H2O
H2O2
color
clear
pale blue
boiling point
100 °C
150 °C
density
1.00 g/mL
1.44 g/mL
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26. Writing Formulas of Compounds
Chemical formulas are abbreviations for compounds.
A chemical formula contains the symbols and ratio of
the atoms of the elements in a compound.
Consider sulfuric acid.
1 molecule contains 2 H atoms, 1 S atom and 4 O atoms.
One possible formula for sulfuric acid is HHSOOOO.
A better formula is H2SO4 – “H-two-S-O-four”.
The numbers after the element symbols are subscripts.
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27. Writing Formulas of Compounds
The formula of a compound contains the symbols
of all the elements in the compound.
When a formula contains only one atom of an element,
the number 1 is not needed as a subscript.
When a formula contains more than one atom of an
element, the number is indicated by a subscript
written after the symbol.
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28. Writing Formulas of Compounds
When the formula contains more than one of a group
of atoms that occur as a unit, parentheses are placed
around the group and the number of units is
represented by a subscript outside the parentheses.
Formulas show the number and kind of atoms in a
compound, but not the connectivity of the elements.
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29. Let’s Practice! How many of each element is present in K3PO4?
3 K atoms
1 P atom
4 O atoms
How many of each element is present in Mg(OH)2?
1 Mg atom
2 O atoms
2 H atoms
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30. Composition of Compounds
A particular compound always contains the same elements in the same proportions by mass no matter what the origin.
H2O
H2O2
11.2 % H
5.9 % H
88.8 % O
94.1 % O
2 H + 1 O
2 H + 2 O
The Law of Definite Composition states that a compound
always contains two or more elements chemically
combined in a definite proportion by mass.
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31. Composition of Compounds
The Law of Multiple Proportions states that atoms of two
or more elements may combine in different ratios
to produce more than one compound.
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32. Laws and Theories A law is a summary of observed behavior.
A theory or model is an attempt to explain
the observed behavior.
Laws remain constant and do not undergo modification,
while theories sometimes fail and are modified
or discarded over time.
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