chemistry hand out alchemy to chem
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Historical Development of Atom
CONTENTS
1. FROM ALCHEMY TO CHEMISTRY
2. THE GREEK’S IDEA ABOUT THE ATOM
3. THE MODERN SCIENTISTS’ IDEA OF THE ATOM
4. THE NUCLEAR MODEL IN FOCUS
5. THE MAIN IDEAS IN THE DISCOVERY OF THE ATOMIC STRUCTURE AND ITS
SUBATOMIC PARTICLE
FROM ALCHEMY TO CHEMISTRY
The word “alchemy” brings to mind witches stirring a
boiling pot, or sorcerers in smoky labs. Despite these
magical images, alchemy led to how science is
practiced today.
Alchemy was an early philosophical and spiritual field
of study. It combined chemistry with metalwork. But it
also explored how nature works. Alchemy brought
together physics, medicine, astrology, mysticism,
spiritualism, and art.
The goals of alchemy were:
• to find the “elixir of life.” It was thought that this
magical potion would bring wealth, health, and
eternal life;
• to find or make a substance called the
“philosopher’s stone.” Alchemists thought gold was
the purest form of matter. They believed if they
combined the “stone” with copper or iron it would
create gold; and
• to discover the relationship of humans to the
cosmos. With that knowledge, alchemists wanted to
improve the human spirit.
Alchemy was scientific, but it was also spiritual. Some who practiced it had good hearts. Alchemists
wanted to learn the secret of “purifying” copper or iron into gold. If they could accomplish this, they
thought they might be able to purify the human soul. At the same time, alchemists were often seen as
fakes. But many alchemists were in fact serious about their work. What they accomplished helped lay
the building blocks for modern chemistry and medicine.
THE CENTRAL SCIENCE
Alchemy began as a quest to know the world around us. That quest for knowledge required an
understanding of how chemicals worked. Alchemy itself died out during the 1700s with the rise of
modern science. Yet, the quest it began continues today in chemistry. Chemistry is sometimes called
“the central science.” It connects sciences like physics, geology, and biology. To understand the field of
chemistry, we must start at the beginning.
Alchemists contributed to many future uses of chemicals like metalwork, paints and cosmetics. These
contributions enriched the societies in which alchemists lived. They even helped advance civilization.
But alchemists often saw no difference between their work with chemicals and what we might call
magic. They borrowed symbols and words from the Bible and myths. Even the simplest formula read
like a magic spell. And although there were commonly used practices, alchemists had no standards that
they all used.
FROM ALCHEMY TO CHEMISTRY
Chemistry Timeline
Ancient Alchemy 3000 B.C. to 800 A.D.
• c. 3000 B.C. – Egyptians formulate the theory of the Ogdoad, or the “primordial forces”, from which
all was formed. These were the elements of chaos that existed before the creation of the sun
• c. 1900 B.C. – Hermes Trismegistus, semi-mythical Egyptian king, who is supposed to have founded
of the art of alchemy
• c. 450 B.C. – Empedocles asserts that all things are composed of four primal elements – earth, air,
fire, and water, whereby two active and opposing forces, love and hate, or affinity and antipathy, act
upon these elements, combining and separating them into infinitely varied forms
• c. 440 B.C. – Democritus propose the idea of the atom, an indivisible particle that all matter is
made of • c. 360 B.C. – Plato coins term ‘elements’ and postulates that the minute particle of each
element had a special geometric shape – tetrahedron for fire; octahedron for air; icosahedron for
water; and cube for earth)
• c. 350 B.C. – Aristotle articulates his theory of the Five Elements, fire, water, earth, air, and ether
• 0 A.D. – Common Era after the Birth of Christ Begins
• c. 300 – Zosimos of Panopolis writes some of the oldest known books on alchemy
Classical Alchemy 800 A.D. to 1661
• c. 815 – Abu Musa Jabir ibn Hayyan isolates numerous acids, including hydrochloric acid, nitric
acid, citric acid, acetic acid, tartaric acid, and aqua regia
• c. 900 – Abū Bakr Muhammad ibn Zakarīya al-Rāzi publishes several treatises on chemistry,
including some of the earliest descriptions of controlled distillation and extraction methods
• c. 1220 – Robert Grosseteste publishes several Aristotelian commentaries where he lays out an
early framework for the scientific method
• c. 1267 – Roger Bacon publishes Opus Maius, proposing the scientific method and results of his
experiments with gunpowder
• c. 1530 – Paracelsus developes the study of iatrochemistry, a subdiscipline of alchemy dedicated to
extending the life
• 1597 – Andreas Libavius publishes Alchemia, a prototype chemistry textbook • 1605 – Sir Francis
Bacon publishes The Proficience and Advancement of Learning, containing an outline of the scientific
method
• 1605 – Michał Sędziwój publishes the alchemical treatise A New Light of Alchemy, proposing the
existence of the "food of life" within air
• 1615 – Jean Beguin publishes the early chemistry textbook, Tyrocinium Chymicum, with the first-
ever chemical equation
• 1637 – René Descartes publishes Discours de la Méthode, containing an outline of the scientific
method
• 1648 – Publication of the Johann Baptista van Helmont’s book Ortus Medicinae a major transitional
work between alchemy and chemistry, and which also influences Robert Boyle. The book shows the
results of experiments and establishes an early version of the Law of Conservation of Mass
FROM ALCHEMY TO CHEMISTRY
The Modern Chemistry Era 1661 to Present
• 1661 – Robert Boyle publishes The Sceptical Chymist, a treatise on the distinction between
chemistry and alchemy
• 1662 – Robert Boyle proposes Boyle's Law on the behavior of gases
• 1754 – Joseph Black isolates carbon dioxide
• 1758 – Joseph Black formulates the concept of latent heat to explain the thermochemistry of
phase changes
• 1773-1774 – Carl Wilhelm Scheele and Joseph Priestly independantly isolate oxygen
• 1778 – Antoine Lavoisier recognizes and names oxygen, and recognizes its importance and
role in combustion
• 1787 – Antoine Lavoisier publishes Méthode de Nomenclature Chimique, the first modern
system of chemical nomenclature
• 1787 – Jacques Charles proposes a corollary to Boyle’s Law, which he names Charles's Law,
describing the relationship between temperature and volume of a gas
• 1789 – Antoine Lavoisier publishes the first modern chemistry textbook, Traité Élémentaire
de Chimie
• 1797 – Joseph Proust proposes Law of Definite Proportions, which states that elements
always combine in small, whole number ratios to form compounds
• 1800 – Alessandro Volta makes the first chemical battery
• 1803 – John Dalton proposes Dalton's Law, which describes relationship between the
components in a mixture of gases and the relative pressure each contributes to that of the
overall mixture
• 1805 – Joseph Louis Gay-Lussac discovers that water is composed of two parts hydrogen
and one part oxygen
• 1807-1808 – Sir Humphry Davy uses electrolysis to isolate numerous elements, including
potassium, sodium, calcium, strontium, barium, chlorine and the first discovery of aluminum
• 1808 – John Dalton publishes New System of Chemical Philosophy, which contains first
modern scientific description of the atomic theory
• 1808 – Jöns Jakob Berzelius publishes Lärboki Kemien in which he proposes modern
chemical symbols and notation, and of the concept of relative atomic weight
• 1811 – Amedeo Avogadro proposes Avogadro's law, that equal volumes of gases contain
equal numbers of particles
• 1825 – Michael Faraday isolates benzene
• 1828 – Friedrich Wöhler synthesizes urea, thereby establishing that organic compounds
could be produced from inorganic starting materials, disproving the theory of “vital life force”
• 1840 – Germain Hess proposes Hess's Law, an early statement of the Law of conservation of
energy
• 1847 – Hermann Kolbe obtains acetic acid from completely inorganic sources • 1848 – Lord
Kelvin establishes concept of absolute zero, the temperature at which all molecular motion
ceases
• 1849 – Louis Pasteur discovers chirality and in tartaric acid, starting the study of
stereochemistry
• 1855 – Benjamin Silliman, Jr. pioneers methods of petroleum cracking, which makes the
entire modern petrochemical industry possible
FROM ALCHEMY TO CHEMISTRY
• 1856 – William Henry Perkin synthesizes the first synthetic dye
• 1862 – Alexander Parkes exhibits Parkesine, one of the earliest synthetic polymers
• 1865 – Friedrich August Kekulé von Stradonitz establishes structure of benzene as a six carbon ring
• 1865 – Adolf von Baeyer begins work on indigo dye, a milestone in modern industrial organic chemistry
which revolutionizes the dye industry
• 1869 – Dmitri Mendeleev publishes the first modern periodic table
• 1883 – Svante Arrhenius developes ion theory to explain conductivity in electrolytes
• 1884 – Henry Louis Le Chatelier develops Le Chatelier's principle, which explains the response of
dynamic chemical equilibria to external stresses
• 1894-1898 – William Ramsay discovers the noble gases
• 1903 – Mikhail Semyonovich Tsvet invents chromatography
• 1905 – Fritz Haber and Carl Bosch develop the Haber process for making ammonia
• 1907 – Leo Hendrik Baekeland inventes bakelite, one of the first commercially successful plastics
• 1909 – Ernest Rutherford, Hans Geiger, and Ernest Marsden perform the Gold foil experiment, which
proves the nuclear model of the atom, with a small, dense, positive nucleus surrounded by a diffuse
electron cloud
• 1909 – Robert Millikan performs the Oil drop experiment, which confirms the existence of electron as
the quanta of electric charge, and determines charge/mass ratio of an electron
• 1909 – S. P. L. Sørensen invents the pH concept and develops methods for measuring acidity • 1912 –
William Henry Bragg and William Lawrence Bragg proposes Bragg's law and establishes the field of X-ray
crystallography
• 1913 – Niels Bohr introduces concepts of quantum mechanics to atomic structure by proposing what is
now known as the Bohr model of the atom
• 1913 – Frederick Soddy proposes the concept of isotopes, that elements with the same chemical
properties may have differing atomic weights
• 1916 – Gilbert N. Lewis publishes The Atom and the Molecule, the foundation of valence bond theory
• 1921 – Otto Stern and Walther Gerlach establish concept of quantum mechanical spin in subatomic
particles
• 1923 – Gilbert N. Lewis and Merle Randall publish Thermodynamics and the Free Energy of Chemical
Substances, first modern treatise on chemical thermodynamics
• 1923 – Gilbert N. Lewis develops the electron pair theory of acid/base reactions
• 1935 – Wallace Carothers leads a team of chemists at DuPont who invent nylon
• 1932 – Linus Pauling first describes the property of electronegativity as a means of predicting the dipole
moment of a chemical bond
• 1937 – Carlo Perrier and Emilio Segrè perform the first confirmed synthesis of technetium-97, the first
artificially produced element
• 1937 – Eugene Houdry develops a method of industrial scale catalytic cracking of petroleum, leading to
the development of the first modern oil refinery
• 1939 – Linus Pauling publishes The Nature of the Chemical Bond, one of the most important modern
chemical texts
• 1945-1946 – Felix Bloch and Edward Mills Purcell develop the process of Nuclear Magnetic Resonance,
an analytical technique important in elucidating structures of molecules, especially in organic chemistry
• 1952 – Robert Burns Woodward, Geoffrey Wilkinson, and Ernst Otto Fischer discover the structure of
ferrocene, one of the founding discoveries of the field of organometallic chemistry • 1962 – Neil Bartlett
synthesizes xenon hexafluoroplatinate, showing for the first time that the noble gases can form chemical
compounds
• 1985 – Harold Kroto, Robert Curl and Richard Smalley discover fullerenes, a class of large carbon
molecules superficially resembling the geodesic dome designed by architect R. Buckminster Fuller
• 1995 – Eric Cornell and Carl Wieman produce the first Bose–Einstein condensate, a substance that
displays quantum mechanical properties on the macroscopic scale
THE GREEK’S IDEA ABOUT THE ATOM
ARISTOTLE and PLATOAristotle was a very famous Greek philosopher whobelieved that matter could be divided into smaller andsmaller pieces forever. He held a very strong influence onpopular belief and his views on this were accepted for twothousand years. Aristotle and Plato favored the earth,
fire, air and water approach to the nature of matter.
He thought matter is like motion.
It cannot be divided in half forever.
The tortoise and hare would never finish the race if you could keep
dividing the distance to the finish line in half forever.
LEUCIPPUS AND DEMOCRITUS
Democritus was an ancient Greek philosopher who lived from 460 - 370 B.C.
His teacher was Leucippus.
What did Democritus and Leucippus conclude about cutting matter in half?
There was a limit to how far you could divide matter. You would eventually
end up with a piece of matter that could not be cut which he termed as
“atomos” – uncuttable and indestructible.
To Democritus, atoms were small, hard particles that were all made of the same
material but were different shapes and sizes. Atoms were infinite in number, always
moving and capable of joining together.
This theory was ignored and forgotten for more than 2000 years!!! Why?
The eminent philosophers of the time, Aristotle and Plato, had a more respected, (and
ultimately wrong) theory.
EMPEDOCLESAristotle was a very famous Greek philosopher whobelieved that matter could be divided into smaller andsmaller pieces forever. He held a very strong influence onpopular belief and his views on this were accepted for twothousand years. Aristotle and Plato favored the earth,
fire, air and water approach to the nature of matter.
THE MODERN SCIENTISTS’ IDEA OF THE ATOM
Dalton expressed his theory in a series of postulates. Like most great thinkers, he
integrated the ideas of others into his own.
1. All matter consists of atoms, tiny indivisible particles of an element that cannot be
created nor destroyed. (This is derived from the “eternal, indestructible atoms”
proposed by Democritus more than 2000 years earlier and reflects mass
conservation as stated by Lavoisier)
2. Atoms of one element cannot be converted into atoms of another element, In
chemical reactions, the atoms of the original substances recombine to form
different substances. (This rejects the belief in the magical transmutation of
elements that was widely held into the 17th century.)
3. Atoms of an element are identical in mass and other properties and are different
from atoms of any other element. (This contains Dalton’s major new ideas: unique
mass ad properties for the atoms of a given element.)
4. Compounds result from the chemical combination of a specific ration of atoms of
different elements. (This follows directly from the law of definite composition.)
JOHN DALTONTwo thousand years later a British chemist and schoolteacher brings back
Democritus’s idea of the atom. He performed many experiments to study how
elements join together to form new substances. He found that they combine in
specific ratios (remember the electrolysis of water) and he supposed it was
because the elements are made of atoms.
JOSEPH JOHN THOMSONIn 1897, the English scientist J.J. Thomson provided the first hint that an atom is
made of even smaller particles. He proposed a model of the atom called the
“Raisin Bread/Bun Model” that is sometimes called the “Plum Pudding” model.
Atoms were made from a positively charged substance with negatively charged
electrons scattered about, like raisins in a pudding.
Thomson concluded that the negative charges came from
within the atom. A particle smaller than an atom had to exist.
The atom was divisible!
Thomson studied the passage of an electric current
through a gas. As the current passed through the gas, it
gave off rays of negatively charged particles.
This surprised Thomson, because the atoms of the gas were
uncharged. Where had the negative charges come from?
Thomson called the negatively charged “corpuscles,” today known as electrons.
Since the gas was known to be neutral, having no charge, he reasoned that there must
be positively charged particles in the atom. But he could never find them.
THE MODERN SCIENTISTS’ IDEA OF THE ATOM
ERNEST RUTHERFORDIn 1908, the English physicist Ernest Rutherford was hard at work on an
experiment that seemed to have little to do with unraveling the mysteries of the
atomic structure.
Rutherford’s experiment involved firing a stream of tiny positively charged
particles at a thin sheet of gold foil (2000 atoms thick).
This could only mean that
the gold atoms in the
sheet were mostly open
space. Atoms were not a
pudding filled with a
positively charged
material. Rutherford
concluded that an atom
had a small, dense,
positively charged center
that repelled his positively
charged “bullets.”
He called the center of the
atom the “nucleus”
The nucleus is tiny
compared to the atom as
a whole.
Most of the positively charged “bullets” passed right through the
gold atoms in the sheet of gold foil without changing course at
all. Some of the positively charged “bullets,” however, did bounce
away from the gold sheet as if they had hit something solid. He
knew that positive charges repel positive charges.
Rutherford reasoned that all of an atom’s positively charged
particles were contained in the nucleus. The negatively charged
particles were scattered outside the nucleus around the atom’s
edge. His proposed model of the atom is called the “nuclear model”.
NEILS BOHRIn 1913, the Danish scientist Niels Bohr proposed an
improvement. In his model, he placed each electron in
a specific energy level.
According to Bohr’s atomic model, “Planetary Model”,
electrons move in definite orbits around the nucleus,
much like planets circle the sun. These orbits, or
energy levels, are located at certain distances from
the nucleus.
THE NUCLEAR MODEL IN FOCUS
RUTHERFORD’SNUCLEAR MODEL OF AN ATOM
Mostly empty space
Small, positive nucleus
Contained protons
Negative electrons scattered around the
outside
Subatomic Particles Location
ElectronsOutside nucleus
(energy levels)
Protons Nucleus
Neutrons Nucleus
THE MAIN IDEAS IN THE DISCOVERY OF THE ATOMIC STRUCTURE
AND ITS SUBATOMIC PARTICLEThe idea of atom, “atomism”, was first proposed by the ancient Greek philosopher
Democritus. His idea was ignored for about 2000 years because the idea of eminent philosophers,
Aristotle and Plato, was favored due to their influence on public belief.
Democritus was justified by John Dalton by adopting his idea and proposed the
atomic theory. The first model of the atom, the “Solid Sphere Model”, was proposed by Dalton. He
opened the revolution on the study of atom. There were more atomic theories proposed and the
development of the atomic structure persisted.
Consequently, Joseph John Thomson discovered the electron by working in an
experiment involving the use of cathode ray tube. With this, he was able to propose his own model
of the atom, the “Plum Pudding Model” or the “Raisin Bun/Bread Model”.
After the discovery of electron, the nucleus was discovered by Ernest Rutherford
through the gold-foil experiment which involved firing a stream of tiny positively charged particles at
a thin sheet of gold foil (2000 atoms thick). His model of the atom is called “Nuclear Model”.James Chadwick discovered the neutron using evidence collected by Irene Joliot-Curie, who
discovered that when beryllium was bombarded with positively charged alpha particles a beam with a highpenetrating power was created. James Chadwick discovered that this beam was not deflected by eitherelectric or magnetic fields, meaning it contained neutral particles- neutrons. Neutrons were found to havethe same mass as protons which accounted for more of the mass of the atom and allowed the masses (theknownmass of an atom and the knownmass of its particles) to match.
The common understanding of an atom was now a nucleus containing positively chargedprotons and neutral neutrons (making up nearly all of the atom's mass) with the rest of the atom (most of it-considering the relative size of the nucleus, which was found to have a radius of10000 times less than theatom itself) being space in which negatively charged electrons (with a mass so small it is insignificantcompared to that of the nucleus) "orbit" the nucleus on energy levels corresponding to the amount of energythe electrons hold.
REFERENCES:
• https://www.ambrosevideo.com/resources/documents/Timeline%20for%20Core%20Ch
emistry.pdf
• https://school.bighistoryproject.com/media/khan/articles/U3_From_Alchemy_to_Chemi
stry_2014_810Lindd.pdf
• https://sites.google.com/site/historyofanatom/james-chadwick
• http://www.chymist.com/History%20Alchemy.pdf