Democritus and Leucippus

Everything existing in the universe is the fruit of

chance and necessity. 

Atomic Hypothesis

Democritus Leucippus

He was a (born c. 460 — died c. 370 BC) Greek philosopher.

• He was an Ancient Greek Philosopher born in Abdera, Thrace in Greece.

Leucippus was his mentor.

• Yuh. Democritus.

Leucippus or Leukippos was one of the earliest Greeks to develop the theory of atomism

• He was born in Miletus and spent the rest of his life in Abdera.

Democrituswas his student.

• Yuh. Leucippus.

held that everything is composed of "atoms“ “Atoms” are physically, but not geometrically,

indivisible. that between atoms lies empty space; that

atoms are indestructible;  have always been, and always will be, in motion that there are an infinite number of atoms There are different kinds of atoms, which differ

in shape, and size. Democritus said "The more any indivisible

exceeds, the heavier it is." But his exact position on weight of atoms is disputed.

The Atomistic Philosophy of Leucippus and Democritus

ROBERT BOYLE And I might add the confidence with which distracted persons do oftentimes, when they are awake, think, they see black fiends in places, where there is no black object in sight without them. Robert Boyle

Atomic Theory ROBERT BOYLE

Robert Boyle FRS (25 January 1627 – 31 December 1691) was a 17th century natural philosopher, chemist, physicist, and iventor, also noted for his writings in theology.He is best known for Boyle's law.

Boyle is best remembered for Boyle's law, a physical law that explains how the pressure and volume of a gas are related.

He advanced the view that the basic elements of matter are "corpuscles," or particles, of various sorts and sizes. Boyle believed that these corpuscles were capable of arranging themselves into groups, and that each group constituted a chemical substance. 

He successfully distinguished between mixtures (substances mixed together) and compounds (chemically bonded substances) and showed that a compound can have very different qualities from those of its constituents.

Antoine LavoisierI consider nature a vast chemical laboratory in which all kinds of composition and decompositions are formed. Antoine Lavoisier 

Born: 26 August 1743Birthplace: Paris, FranceDied: 8 May 1794 (beheading)Best Known As: French chemist who

proved the law of conservation of mass

Because of his achievements he is sometimes called the father of modern chemistry.

Antoine Lavoisier’s contribution to atomic theory

Antoine Lavoisier was the first person to make good use of the balance. 

After a visit with Priestly in 1774, he began careful study of the burning process.  He proposed the Combustion Theory which was based on sound mass measurements. 

He named oxygen.He also proposed the Law of Conversation

of Mass which represents the beginning of modern chemistry.

Joseph Proust

 Joseph L. Proust was born on September 26,

1754 in Angers, France.

Under Carlos IV’s influence Proust went toSpain. There he taught at the Chemistry School in Segovia and at the University of Salamanca. But when Napoleon invaded Spain, they burned Proust's laboratory and forced him back to France. On July 5 1826 he died in Angers, France..

Joseph Proust

Joseph Proust proposed the the Law of Constant Composition in 1799.

 Law of Definite Proportions ( also called Law

of Constant Composition) –states that a given compound always has the same elements in the same proportion by mass. 

J. Berzelius (Jöns Jacob Berzelius)

Jöns Jacob Berzelius  (20 August 1779 – 7 August 1848) was a Swedish chemist. He worked out the modern technique of chemical formula notation, and is together with John Dalton, Antoine Lavoisier, and Robert Boyle considered a father of modern chemistry.

J. Berzelius (contribution)

The most notable of Berzelius's contributions to chemistry was his development of a rational system of atomic symbols.

Around 1810 Berzelius was working to confirm John Dalton's atomic theory as well as Proust's law showing that separate elements always combined in whole-number proportions. 

Berzelius came to the conclusion that the existing system of denoting elements and compounds was a hindrance. In establishing his own atomic symbols,

He stated that "it is easier to write an abbreviated word than to draw a figure which has little analogy with words" Berzelius opted to use the first letter of the Latin name for each element as its symbol.

John Dalton (6 September 1766 – 27 July 1844) was an English chemist, meteorologist and physicist. He is best known for his pioneering work in the development of modern atomic theory, and his research into colour blindness (sometimes referred to as Daltonism, in his honour).

John Dalton

All matter is made of atoms. Atoms are indivisible and indestructible.

All atoms of a given element are identical in mass and properties

Compounds are formed by a combination of two or more different kinds of atoms.

 A chemical reaction is arearrangement of atoms.

Dalton's Atomic Theory

J.J Thomson

•Sir Joseph John "J. J." Thomson,  (18 December 1856 – 30 August 1940) was aBritish physicist and Nobel laureate.

•He is credited for the discovery of the electron and of isotopes, and the invention of the ,mass spectrometer.

•“To the electron: may it never be of any

use!'' 

JJ Thomson's major contributions to the atomic theory..

• His atomic theory identified that electrons inside an atom could show, meaning that atoms were not invisible. Thomson suggested that the model of an atom as a sphere of positively charged matter with negatively charged electrons surrounding them.

• He stated that electrons were positioned by electrostatic forces.

• After the discovery of the electron and proton as subatomic particles J.J. Thomson had started to discover atomic theory that gives complete explanation of atomic structure.According to Thomson protons are embed in the atoms like a water melon and electrons are present in atoms to make the atom electrically neutral.

ERNEST RUTHERFORD

Ernest Rutherford, 1st Baron Rutherford of Nelson (30 August 1871 – 19 October 1937) was a New Zealand-born British chemist and physicist who became known as the father of nuclear physics

He was awarded in 1908 "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances".

RUTHERFORD'S ATOMIC THEORY - ELECTRONEGATIVITY Ernest Rutherford publishes his atomic theory

describing the atom as having a central positive nucleus surrounded by negative orbiting electrons.

Rutherford came to this conclusion following the results of his famous gold foil experiment.

 Rutherford found that although the vast majority of particles passed straight through the foil approximately 1 in 8000 were deflected leading him to his theory that most of the atom was made up of 'empty space'.

Niels Bohr

Niels Henrik David Bohr (October 1885 – November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922.

Bohr’s Atomic Theory Neils Bohr postulated based on quantum theory

that electrons travel around an atomic nucleus in a stationary orbit.

Relegates the number of valence electrons to the Periods of a periodic table

Fully explains ionic and covalent bonding His work also led to the theory of different energy

levels in atoms, that is if an electron drops from a higher to a lower orbit, it must release energy.