Development of the Atom

VIDEO ON DEMAND Moving through history, this program progresses from the ancient to the modern view of the atom and its applications in new technology. Viewers will journey inside the atom to appreciate its architectural beauty and grasp how atomic structure determines chemical behavior. World of Chemistry The Annenberg Film Series Episode 6Episode 6 – Atom

The Hellenic Market FireWater Earth Air ~ ~

In fourth century B.C., ancient Greeks proposed that matter consisted of fundamental particles called atoms. Over the next two millennia, major advances in chemistry were achieved by alchemists. Their major goal was to convert certain elements into others by a process called transmutation. A Brief History of Chemistry Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

The Greeks History of the Atom Not the history of atom, but the idea of the atom In 400 B.C the Greeks tried to understand matter (chemicals) and broke them down into earth, wind, fire, and air. Democritus and Leucippus Greek philosophers  

Greek Model Greek philosopher Idea of ‘democracy’ Idea of ‘atomos’ –Atomos = ‘indivisible’ –‘Atom’ is derived No experiments to support idea Continuous vs. discontinuous theory of matter Democritus’s model of atom No protons, electrons, or neutrons Solid and INDESTRUCTABLE Democritus “To understand the very large, we must understand the very small.”

DEMOCRITUS (400 BC) – First Atomic Hypothesis Atomos: Greek for “uncuttable”. Chop up a piece of matter until you reach the atomos. Properties of atoms: indestructible. changeable, however, into different forms. an infinite number of kinds so there are an infinite number of elements. hard substances have rough, prickly atoms that stick together. liquids have round, smooth atoms that slide over one another. smell is caused by atoms interacting with the nose – rough atoms hurt. sleep is caused by atoms escaping the brain. death – too many escaped or didn’t return. the heart is the center of anger. the brain is the center of thought. the liver is the seat of desire. “Nothing exists but atoms and space, all else is opinion”. Democritus

Mental Experiment – Atoms Exist Looked at beach Made of sand Cut sand - smaller sand  Smallest possible piece?  Atomos - not to be cut

Four Element Theory Plato was an atomist Thought all matter was composed of 4 elements: –Earth (cool, heavy) –Water (wet) –Fire (hot) –Air (light) –Ether (close to heaven) ‘MATTER’ FIRE EARTHAIR WATER Hot Wet Cold Dry Relation of the four elements and the four qualities Blend these “elements” in different proportions to get all substances

Anaxagoras Anaxagoras (Greek, born 500 B.C.) seeds –Suggested every substance had its own kind of “seeds” that clustered together to make the substance, much as our atoms cluster to make molecules. Some Early Ideas on Matter O’Connor Davis, MacNab, McClellan, CHEMISTRY Experiments and Principles  1982, page 26, Empedocles Empedocles (Greek, born in Sicily, 490 B.C.) – earth, air, fire, and water –Suggested there were only four basic seeds – earth, air, fire, and water. The elementary substances (atoms to us) combined in various ways to make everything. Democritus (Thracian, born 470 B.C.) proposed the word atom –Actually proposed the word atom (indivisible) because he believed that all matter consisted of such tiny units with voids between, an idea quite similar to our own beliefs. It was rejected by Aristotle and thus lost for 2000 years. Aristotle Aristotle (Greek, born 384 B.C.) – heat, cold, dryness, moisture – as basic elements –Added the idea of “qualities” – heat, cold, dryness, moisture – as basic elements which combined as shown in the diagram (previous page). Hot + dry made fire; hot + wet made air, and so on.

Who Was Right? Greek society was slave based Beneath famous to work with hands did not experiment Greeks settled disagreements by argument Aristotle was more famous He won! His ideas carried through middle ages. Alchemists change lead to gold

Alchemy After that chemistry was ruled by alchemy. They believed that that could take any cheap metals and turn them into gold. Alchemists were almost like magicians. –elixirs, physical immortality

Alchemy GOLDSILVERCOPPER IRONSAND Alchemical symbols for substances… transmutation: changing one substance into another In ordinary chemistry, we cannot transmute elements. 

Contributions of alchemists: Information about elements - the elements mercury, sulfur, and antimony were discovered - properties of some elements Develop lab apparatus / procedures / experimental techniques - alchemists learned how to prepare acids. - developed several alloys - new glassware

Early Ideas on Elements Robert Boyle stated... –A substance was an element unless it could be broken down to two or more simpler substances. –Air therefore could not be an element because it could be broken down in to many pure substances. Robert Boyle

Beginnings of modern chemistry were seen in the sixteenth and seventeenth centuries, where great advances were made in metallurgy, the extraction of metals from ores. In the seventeenth century, Boyle described the relationship between the pressure and volume of air and defined an element as a substance that cannot be broken down into two or more simpler substances by chemical means. Modern Chemistry Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

 During the eighteenth century, Priestley discovered oxygen gas and the process of combustion where carbon-containing materials burn vigorously in an oxygen atmosphere.  In the late eighteenth century, Lavoisier discovered respiration and wrote the first modern chemistry text. His most important contribution was the law of conservation of mass, which states that in any chemical reaction, the mass of the substances that react equals the mass of the products that are formed. He is known as the father of modern chemistry. Modern Chemistry Copyright © 2007 Pearson Benjamin Cummings. All rights reserved. Priestley Lavoisier

Timeline AD American Independence (1776) Issac Newton ( ) 400 BC Greeks (Democritus ~450 BC) Discontinuous theory of matter ALCHEMY Greeks (Aristotle ~350 BC)) Continuous theory of matter