Brief History of Chemistry
Chemistry from “Khemeia”
• By 4000 BCE, in Egypt and Sumeria
(Iraq), metals such as copper and
gold were being used.
• These were valuable because the
metal could be shaped (malleable)
and could keep an edge.
• In addition to metallurgy Egypt also
developed embalming and dying
• The Greeks named this learning
Khemeia from Khumos, juice of
plants
Democritus – all matter is made of small,
indivisible particles called “atomos”
Ancient Greeks
• Democritus
• 460 BCE to 370 BCE
• was a student of Leucippus
and co-originator of the
belief that all matter is made
up of various imperishable,
indivisible elements
• He called these atoma (sg.
Atomon) or "indivisible units"
Aristotle – matter is continuous and
NOT made of smaller particles
Ancient Greeks
• Plato and Aristotle
• Aristotle (384 BCE to
332BCE)
• Believed there were 4
classic elements
– Earth, fire, water, air
• Alexander 323 BCE conquered Egypt.
Under Ptolemy Greek-Egyptian Khemeia
took hold. Mixed religion and learning.
• Khemeia declined under the Romans
who had no use for this mixture of
mysticism and craft
• 500 years of Arab dominated learning
650 - 1100 CE. Khemeia became AlChemi
The “Age of Discovery” was start
of true science.
Age of Discovery
• The discovery of the new world not described by the
Greeks and improvements in navigation allowed
Europeans to doubt the wisdom of the ancients and
opened the way to the acceptance of new ideas.
• The invention of the printing press in 1436 by Johann
Gutenberg made the dissemination of new ideas to
larger numbers possible.
Alchemy not science
Alchemy
• ~ 1600 ACE
• Mystical pseudoscience
• Searched for
“philosopher’s stone”
• Some goals were
transmutation, panacea
and universal solvent
1st true “chemist”
Discovered a relationship between
pressure and volume (Boyle’s Law)
Robert Boyle
Developed the “scientific
method” where
experiments were devised
to test theories.
Defined an ‘element’ as
something unable to be
broken down into simpler
substances.
~1660
1st Developed the Law of
Conservation of Mass.
Developed the theory of combustion.
Determined the composition of water.
Antoine Laurent Lavoisier
Lavoisier was a French
nobleman and chemist
central to the 18th-century
Chemical Revolution and a
large influence on both the
histories of chemistry and
biology. He is widely
considered to be the "Father
of Modern Chemistry.”
~1770
Antoine Laurent Lavoisier
It is generally accepted that Lavoisier's great
accomplishments in chemistry largely stem from the fact
that he changed the science from a qualitative to a
quantitative one. Lavoisier is most noted for his discovery of
the role oxygen plays in combustion. He recognized and
named oxygen (1778) and hydrogen (1783). Lavoisier
helped construct the metric system, wrote the first extensive
list of elements, and helped to reform chemical
nomenclature.
He discovered that, although matter may change its form or
shape, its mass always remains the same.
Found that a given compound always
contains exactly the same proportion of
elements by mass - Law of Definite
Proportions
Joseph Louis Proust
Joseph Louis Proust (September 26, 1754
– July 5, 1826) was a French chemist. He
discovered the law of definite proportions,
which states that every chemical
compound contains fixed and constant
proportions by weight of its constituent
elements (law). Proust worked with many
chemical compounds and still found that
no matter where the compound came
from or how it was produced, it had the
same composition.
The ratios of the masses of elements in a
compound can always be reduced to small
whole numbers – Law of Multiple Proportions
John Dalton - 1800
If two elements form more
than one compound between
them, then the ratios of the
masses of the second element
which combine with a fixed
mass of the first element will
be ratios of small whole
numbers.
Atomic Theory
John Dalton - Atomic Theory
1) all matter is composed of tiny particles called
atoms
2) the atoms of an element are always identical
while the atoms of different elements are
different
3) compounds form when atoms combine;
atoms combine in small whole number ratios
4) reactions involve reorganization of atoms;
the atoms themselves do not change
The ratios of the masses of elements in a
compound can always be reduced to small
whole numbers – Law of Multiple Proportions
John Dalton –Billiard Ball Model
John Dalton (1766 – 1844) proposed a basic
model of the atom that helped establish many
scientific concepts and also created the foundation
for more modern models. His model suggested
that atoms are the smallest particle of an element,
that atoms of different elements have different
masses, and that they are solid, indestructible
units - much like a billiard ball.
Equal volumes of gases at the same
temperature and pressure contain the same
number of molecules regardless of their
chemical nature and physical properties.
- Avogadro's Law
Amadeo Avogadro - 1808
Avogadro's Law states that the relationship
between the masses of the same volume of
different gases (at the same temperature and
pressure) corresponds to the relationship between
their respective molecular weights. Hence, the
relative molecular mass of a gas can be calculated
from the mass of sample of known volume.
The Avogadro constant (6.02214X×1023) is named
after the early 19th century Italian scientist as an
honor.
Constructed first workable Periodic Table
Dmitri Mendeleev - 1869
Constructed a periodic table by
arranging elements:
•in order of increasing atomic mass
•in vertical groups based on similar
chemical properties
He left gaps for undiscovered
elements and reversed the order of
some elements to make their
chemical properties fit.
Lothar Meyer - 1870
Also constructed a
periodic tablesimilar to that of
Mendeleev
Discovered electron (and +1 charge)
Plum Pudding Model
J. J. Thomson - 1897
Discovered that the negative
components of atoms had the same
mass regardless of which element
they came from.
Proposed the ‘plum pudding model of
the atom where negative particles are
dispersed throughout a positively
charged atom.
Marie Curie - 1903
Suggested that radioactive
atoms were unstable and that
energy was emitted during
disintegration
Discovered radium and
polonium
E = mc2
Albert Einstein
Showed that mass
and energy are
interconvertible via:
E = mc²
Proposed the nucleus in an atom and that
atoms are mostly empty space with electrons
in that space
Ernest Rutherford - 1911
Suggested that the atom was
largely space with a very small
but dense centre of positive
charge called the nucleus
Proposed that electrons orbited
the nucleus like planets around
the Sun
Proposed Quantum Physics and electron
energy shells
Niels Bohr - 1913
Proposed that classical
mechanics did not apply
within the atom
Proposed that electrons
orbited the nucleus in shells
of fixed energy
Proposed different shaped
electron orbitals
Arnold Sommerfeld
Expanded the Bohr model
Electrons travel in
orbitals, but
the orbitals are not the
same shape
-- this leads to the electron
cloud model of the atom
Pauli’s Exclusion Principle says no
two electrons do the exact same
thing at the same time
Wolfgang
Pauli
(1924)
Predicted that electrons spin
while orbiting the nucleus
Proposed electron cloud
Erwin Schrödinger - 1926
Developed the wave-like
model of the electron and the
charge cloud model of the
atom
No experiment can measure the
position and momentum of a quantum
particle simultaneously
- Heisenberg’s Uncertainty Principle
Werner Heisenberg
The Heisenberg Uncertainty
Principle states that for a very
small particle, such as an
electron, you cannot know
both its exact momentum and
its exact position at the same
time.
Discovered neutron
James Chadwick - 1932
Discovered high
energy particles with
no charge and the
same mass as the
proton –
the neutron