Download Chapter 3 Chemical Foundations: Elements, Atoms, and Ions

Chapter 3
Chemical Foundations:
Elements, Atoms, and
Compounds
3.1 The Elements
We will be doing an activity to learn the
various elements in the periodic table
Assign Elements!
3.2 Atoms and Compounds
Objectives:
1. To learn about Dalton’s theory of atoms
2. To understand and illustrate the Law of
constant composition
3. To learn how a formula describes a
compound’s composition
A. Dalton’s Atomic Theory
What was known about the nature of materials:
1. Most natural materials are mixtures of pure substances.
2. Pure substances are either elements or combinations of
elements- called compounds.
3. A given compound always contains the same proportions (by
mass) of the elements.
Law of constant composition- a given compound always has
the same composition regardless of where it comes from
Dalton’s Atomic Theory:
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 not created or destroyed in chemical
reactions. The atoms will be rearranged differently
after a chemical reaction.
B. Formulas of Compounds
Tools for Writing Formulas:
1. 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, do not write the #1.
Practice
a. A molecule contains four phosphorus atoms
and ten oxygen atoms.
b. A molecule contains one uranium atom and
six fluorine atoms.
c. A compound contains one aluminum atom
for every three chlorine atoms.