Transcript Presentation 2.1

Dalton’s Atomic Theory
by Tiffany, Katelyn, Veronica, Kole
John Dalton (1766-1844)
• John Dalton was born into a Quaker Family.
• Born: September 6th, 1766 in Cumberland, England
• He was an English Meteorologist and then he switched to
study of Chemistry and Physics.
• He proposed the Atomic Theory in 1803
• His theory was presented in New System of Chemical
Philosophy (1808-1827)
• This work identified a specific type of atom, therefore
rejecting Newton’s theory of chemical affinities.
• On a side note, he also researched into color blindness.
For a more in depth biography of John Dalton, please go to this
YouTube Video Link:
http://www.youtube.com/watch?v=sDoH5fPTOfo
Five Main Points of His Atomic Theory
• Elements are made of extremely small particles
called atoms.
• Atoms of a given element are identical in size, mass,
and other properties.
• Atoms cannot be subdivided, created, or destroyed.
• Atoms of different elements combine in simple
whole-number ratios to form chemical compounds.
• In chemical reactions, atoms are combined
separated, or rearranged.
Experiments that led
Dalton to his theory
Key Points:
-He imagined atoms as tiny spheres
- He created a table by looking at the
patterns within the atom
-The table he created is now known as
the “Table of Atomic Weights”
-He furthered his experiment by using his
information from the table.
-He placed each element in a specific
order by their weight, comparing them to
hydrogen, the lightest element.
-Because of this he founded “The Law of
Multiple Proportions”
-He continued his experiment by
experimenting with nitric oxide and
oxygen to see how they reacted with one
another.
-He observed the ratios and proportions
of the two reacting gases
-He continued these experiments to
complete the “Table of Atomic Weights”
- Which therefore concluded much of his
theory.
Dalton used symbols to represent the elements. He
imagined atoms to be tiny spheres, thus to draw atoms
would be to draw circles.
He used patterns within the circles to distinguish the
different elements. Using this way to symbolize
invisible atoms, he could experiment with their
combining properties. He created a “Table of Atomic
Weights” and using the information from this table, he
placed them in a significant order determined by the
weight of the elements, comparing them to hydrogen,
the lightest element, which is number one on the table
and has the atomic number of 1. Dalton discovered the
“Law of Multiple Proportions” and “Law of Definite
Proportions”. These state that the weights of elements
always combine with one another in ratios of small
whole numbers. Dalton experimented with a gas called
nitric oxide (NO) and oxygen (O). He reacted them
together to produce a third type of gas. The results
were determined by the proportions or ratios of the
two reacting gasses.
2NO + O -> N2O3 NO + O -> NO2
Dalton carried out experiments like this, using the law of
multiple proportions, and completed the table of
atomic weights.
Various atoms
and molecules
as depicted in
John Dalton’s
A New System
of Chemical
Philosophy
(1808)
How Does John Dalton’s Atomic
Theory and Research Fit into the
Timeline of Atomic Discovery?
-John Dalton’s first discovery was in 1803
-Considered the father of modern theory, Dalton
was the first in 2000 years to come up with an
atomic theory.
-He continued his research later in 1803
-During the years 1808-1827, he presented his
theory about atoms and their weight in the New
System of Chemical Philosophy
-After his “jump- starting” discovery, many other
scientist started research, such as William
Thomson in 1824- 1907, who was the first to try to
construct a physical model of the atom.
-Scientists’ research has not “missed a beat” in
atomic discovery, since John Dalton.
John Dalton’s Atomic Theory Today
•
•
•
•
•
•
•
Many scientists have expanded upon his theory.
Dalton's new information on atomic weights allowed a Russian chemist, Dmitry
Mendeleyev, to create the periodic table of elements.
Until Dalton, the lines between physics and chemistry was almost unnoticeable, but his
atomic theory distinguished and divided the two disciplines. In physics and chemistry,
the atom is a cornerstone providing an understanding of matter and force, especially in
quantitative analysis.
Dalton's theory was the beginning of nuclear energy and fusion research still used
today.
The theory also provides for the study of the quantitative relationships between
substances in chemical reactions, or stoichiometry. It provides for structural theory and
arrangements of atoms for influencing properties. Dalton's models eventually turned
into the understanding of 3-dimensional qualities of molecules and the affect of
structure on properties. Dalton's theory did have some inaccuracies, but it did provide
the foundation for future generations of scientists.
The parts of his theory that have been proven false are atoms can not be subdivided,
created, or destroyed and atoms are identical in size, mass, and other properties. Atoms
cannot be subdivided was disproven by the splitting of the atom. Also, The theory that
atoms are identical was disproven by the discovery of the neutron.
Much of the theory that was proven false was because John Dalton didn’t know certain
information about the atom because of the technology he had in the time period.