2.
John Dalton 1766-1844
Was an English chemist, meteorologist and
physicist. He is best known for his pioneering
work in the development of modern atomic
theory.
Was born into a Quaker family at Eaglesfield.
In 1800, Dalton became a secretary of the
Manchester Literary and Philosophical Society.
In the following year he orally presented an
important series of papers, entitled
"Experimental Essays" on the constitution of
mixed gases.
3.
John Dalton studied the behavior of gases in
air.
Dalton’s Theory states that all matter is made
up of individual particles called atoms, which
cannot be divided.
All elements are composed of atoms.
All atoms of the same elements have the
same mass, and atoms of different
elements have different masses.
Compounds contain atoms of more than
one element.
In a particular compound, atoms of
different elements always combine in the
same way.
4.
Five Main Points of Dalton’s Atomic
Theory.
1. Elements are made of extremely small particles
called atoms.
2. Atoms of a given element are identical in size,
mass, and other properties; atoms of different
elements differ in size, mass, and other properties.
3. Atoms cannot be subdivided, created, or
destroyed.
4. Atoms of different elements combine in simple
whole-number ratios to form chemical
compounds.
5. In chemical reactions, atoms are combined,
separated, or rearranged.
5.
Dalton proceeded to print his first published
table of relative atomic weights. Six elements
appear in this table, namely hydrogen, oxygen,
nitrogen, carbon, sulfur, and phosphorus, with
the atom of hydrogen conventionally assumed
to weigh 1.
John Dalton’s use of the word “atom” was
influenced by Democritus, Newton and the
Hindu author Kanda.
John Dalton pictures atoms as tiny,
indestructible particles, with no internal
structure.
6.
7.
8.
In summary, John Dalton developed
a theory to explain why the elements
in a compound always join in the
same way. He proposed that all
matter is made up of individual
particles called atoms, which cannot
be divided.
