Chemical Foundations: Elements,
Atoms, and Ions
3.1 The Elements
• Objectives: to learn about the relative abundances of the elements.
• To learn the names of some elements.
• Over 115 known, of which 88 are found
– others are man-made
• Abundance is the percentage found in
– oxygen most abundant element (by
mass) on earth and in the human body
– the abundance and form of an element
varies in different parts of the
3.2 Symbols of the elements
Objective: to learn the symbols of some
• Each element has a unique symbol
• The symbol of an element may be one
letter or two
– if two letters, the second is lower case
3.3 Dalton’s Atomic Theory
Objectives: to learn about Dalton’s theory of atoms. To
understand and illustrate the law of constant composition
1. Elements are made of tiny particles called atoms.
2. All atoms of a given element are identical.
3. The atoms of a given element are different from
those of any other element.
4. Atoms of one element can combine with atoms of
other elements to form compounds. A given
compound always has the same relative numbers
and types of atoms.
5. Atoms are indivisible in chemical processes. That
is, atoms are not created or destroyed in chemical
reactions. A chemical reaction simply changes
the way the atoms are grouped together.
Representation of NO, NO2, and
3.4 Formulas of Compounds
• Objective: To learn how a formula describes a
• a compound isfor distinct substance that is
Rules a Writing Formulas
composed of atoms of two or more elements
Each atom present is represented by its element symbol.
2. The number of each type of atom is indicated by a
subscript written to the right of the element symbol.
3. When only one atom of a given type is present, the
subscript 1 is not written.
4. Polyatomic groups are placed in parentheses
if more than one
•Write the molecular formula for a molecule that contains six atoms of
carbon, 12 atoms of hydrogen and 6 atoms of oxygen.
3.5 The Structure of the Atom
Objectives: To learn about the internal parts of an atom.
To understand Rutherford’s experiment to characterize the
• All types of atoms contain negative particles.
• Atoms must contain positive charges to
balance the negative charges.
• Atom is like plum pudding.
J. J. Thomson - postulated the
existence of electrons using cathode
Figure 2.8: Deflection of cathode rays by an
applied electric field.
Plum Pudding model of an atom.
Atomic Structure: Basic Concepts
The Nuclear Model of the Atom
• To explain the results of the experiment,
Rutherford’s team proposed a new model
of the atom.
• Because most of
the particles passed
through the foil,
they concluded that
the atom is nearly
all empty space.
Click box to view movie clip.
Results of foil experiment if Plum
Pudding model had been correct.
Schematic of a cathode ray tube.
as planets orbit the Sun.
The Gold-Foil Experiment
Objectives: To learn about the terms isotopes,
atomic number, and mass number.
To understand the use of the symbol AZX to
describe a given atom.
• Isotopes: are atoms of the same element with
a different number of neutron in the nucleus.
Most elements in nature are mixtures of
Two isotopes of sodium.
Three Carbon Isotopes
Name Total Protons Total Mass Total
(atomic number) Neutrons Number electrons
Carbon-12 6 6 12 6
Carbon-13 6 7 13 6
Carbon-14 6 8 14 6
• The atomic number of an atom is the number of
protons in its nucleus.
• Mass number = # of neutrons + # of protons
• AZX where X = the symbol of the element
• A = The mass number
• Z = the atomic number (number of protons)
• A=Z+N Number of
1. Write the symbol for the magnesium atom (atomic
number 12) with a mass number of 24. How many
electrons and how many neutrons does this atom
2. Write the symbol for the silver atom (Z=47) that has
3.8 Introduction to the Periodic Table
Objectives: To learn about various features of the periodic table.
To learn some of the properties of metals, nonmetals, and
Periodic table of elements: is the arrangement of
elements according to repeated changes in
• The vertical columns in the periodic table are called
groups, or families.
• The groups are numbered 1 through 18.
• Link to the periodic table:
• The horizontal rows of elements are called periods.
There are 7 periods in the periodic table.
• Lose electrons
• Malleable and ductile
• Ionic bonds
• Gain electrons
• Covalent bonds
Semi-metals or Metalloids
Alkaline Earth Metals
Inner Transition Metals
+3 -3 -2 -1
The periodic table.
– about 75% of all the elements
– lustrous, malleable, ductile, conduct heat and electricity,
they lose electrons, and make metallic and ionic bonds.
– dull, brittle, insulators, they gain electrons, they make
– also known as semi-metals
– some properties of both metals & nonmetals
– such as Silicon that is used in computer chips.
• Alkali metals: are the highly reactive metallic elements
located in Group 1 of the periodic table.
• Alkaline-earth metals: are the reactive metallic elements
located in Group 2 of the periodic table.
• Transition metals: are the metallic
elements located in Groups 3-12 of
the periodic table.
• Halogens: are the highly reactive
elements located in Group 17 of the
• Noble gas or inert gas: are the unreactive
gaseous elements located in Group 18 of
the periodic table.
Properties of Metals Animation
Transition Metal Demo
• Reaction of Sodium and water :
The decomposition of two water molecules.
Objectives: To describe the formation of ions from their parent
atoms, and learn to name them.
To predict which ion a given element forms by using the periodic
table. Ion: is an atom or group of atoms that has lost
or gained one or more electrons and therefore has a
net electric charge.
8e- + 1 e-
11+ - Loses one 11+ 2e-8e-
8e- 8e- 2e 1e- electron
Sodium ion Na+
Neutral sodium atom Na
Cation: is an ion with a positive charge that is
produced when one or more electrons are lost
from a neutral atom.
• Anion: is an ion with a negative charge that is
formed when electrons are gained by a neutral
2e-- Gain one 2e-
17+ 2e- 8e-
2e 2e- electron
Neutral Chloride ion
chlorine atom (Cl-) 18e-
* O + 2e- O2- (oxide ion)
Ion Charges and the Periodic
• Metals form cations
• The charge on a cation can be determined from the
Group number on the Periodic Table for Groups IA,
– Group 1A +1, Group 2A +2, Group 3A +3
• Nonmetals form anions
• The charge on an anion can be determined from the
Group number on the Periodic Table
– Group 7A -1, Group 6A -2
The ions formed by selected members of
groups 1, 2, 3, 6, and 7.
Figure 2.22: The common
cations and anions
3.11 Compounds That Contain
• Objective: to describe how ions combine to
form neutral compounds.
• Ionic compound is a compound that
form between a metal and a nonmetal.
-must have a net charge of zero.
Writing Formulas for Ionic Compounds
Give the formula for each compound
a. Ca2+ and Cl-
b. Na+ and S2-
c. Ca2+ and P3-
Pure water does not conduct a current.
Water containing dissolved salt conducts a
Review for the test
• Write the symbol and find the number of
protons, mass number, number of
electrons, and charge of an ion with
atomic number of 17 and contains 18
neutrons and 18 electrons.
Review for Chapter 3 Test
• Write the formula for the compound that
would be formed from the following ions:
• Al3+ and O2-
• Mg2+ and O2-
• Na+ and S2-
• Pb4+ and O2-
• Phosphorous Video to show for Atomic