Download Atomic Theory

Chapter 2
SC.A.2.4.2., SC.H.1.4.3., SC.H.1.4.5.
Atomic Theory
• atoms are the building blocks of all
matter
•
Idea emerged 2000 years ago
•John Dalton
developed the first
working atomic
theory in 1808
Dalton’s Atomic Theory
1.
All matter is composed of extremely small particles
called atoms, which cannot be subdivided, created, or
destroyed.
*fusion and nuclear reactions disprove this theory.
2. All atoms of a given element are identical in their
physical and chemical properties.
* Isotopes of elements differ in their mass, a
physical property.
Dalton’s Atomic Theory
3. Atoms of different elements differ in their
physical and chemical properties.
4. Atoms of different elements combine in
simple whole number ratios to form
compounds
Dalton’s Atomic Theory
5.
In chemical reactions, atoms are
combined, separated, or rearranged but
never created, destroyed, or changed.
Three laws support the existence of
atoms
1. Law of Definite Proportions:
any two samples of a given compound
are made of exactly the same elements
in exactly the proportions.
2. The law of conservation of mass:
mass cannot be created or destroyed in
ordinary chemical and physical changes
3. The Law of Multiple Proportions:
when two elements combine to form two
or more compounds, the mass of one
element that combines with the given
mass of another element is in the ration
of small whole numbers.
Compound
mass of nitrogen
mass of oxygen
N2O3
28
48
2 NO
28
32