HISTORY OF ATOMS - 2ND LESSON

Democritus period

460-370 BC

Demcritus

• states that all atoms are small, hard, indivisble and indestructable particles of a single material formed into different shapes and sizes (proposed with his mentor leucippus)

• aristole did not support his theory

Antoine Lavoisier period

1743-1744

Antoine Lavoisier

achievments:

• first person to generate a list of 33 elements in his textbook

• proped that combustion occurs when oxygen combines with other elments

• proposed law of conservation of mass (or matter)

Antoine lavoisier 

History:

• known as the “father of modern chemistry”

• married to 13 year old Marie-Anne Pierette Paulze who assisted in his work

• tax collector was guillotined during the french revolution

John Dalton period

1766-1844

John Dalton

Achievements:

• 1803 proposed atomic theory

• calculated the weights of many various elements

John Dalton

History:

• teacher at a very young age

• color blind

J.J Thomson period

1856-1940

J.J Thomson

achievments:

• proved an atom can be divided into small parts

• stated atom as neutral

• won a nobel prize

atomic theory

• all substances are made of atoms

• atoms of the same element are exactly alike and atoms of different elements are different

• atoms joins with other atoms to make new substances (application of chemical bonding and reaction)

atoms

small particles that cannot be created, divided or destroyed (according to john dalton)

J.J Thomson

History:

• 1897, proposed the plum pudding model which states that atoms mostly consist of positively charged material with negatively charged particles (electrons) located throughout the positive material

• experimented with cathode ray tubes and discovered corpules which were later called electrons to prove atoms can be divided into smaller parts

Ernest Rutherford period

1871-1937

Ernest Rutherford

achievements:

• Father of Nuclear Physics

• did extensive work on radioactivity 

Ernest Rutherford

History:

• In 1909, performed the gold foil experiment

• was a student of J.J Thomson

• was the new zealand $100 bill

• won a nobel prize

Characteristics of an atom

• It consists of a small core (nucleus) that contains most of the mass of the atom

• This nucleus is made of particles called protons (postive charge)

• protons are surrounded by negatively charged electons but most of the atom is actually empty space

(According to ernest rutherford)

The Gold Foil Experiment

experiment done by ernest rutherford to prove the characteristics of an atom

Examples of radioactivity

alpha and beta particles, gamma rays/waves

Neil Bhor period

1885-1962

Neil Bhor

• In 1913, proposed the bhor model

• won a nobel prize

• worked with ernest rutherford

Bhor model

suggests that electrons travel around the nucleus of an atom in orbits or definite paths. Additionally, the electrons can jump from a path in one level to a path in another level (depending on their energy)

Erwin Schrodinger period

1887-1961

Erwin Schrodinger

• In 1926, he further explained the nature of electrons in an atom by stating the exact location of an electron cannot be stated; therefore it is more accurate to view electrons in regions called electron clouds; electron clouds are placed where the electrons are likely to be found

• did extensive work on the wave formula “Schrodinger Equation

• won a nobel prize

James Chadwick period

1891-1974

James Chadwick

• realized that the atoms mass of most elements was double the number of protons leading to the discovery of neutron in 1932

• worked on the mahattan project

• worked with ernest rutherford

• won a nobel prize

1803

when atomic theory was proposed

1897

when plum pudding model was proposed

1909

when gold foil experiment suggested the characteristics of an atom

1913

when bhor model was proposed

1926

when erwin schrodinger explained the nature of electrons in an atom

1932

discovery of the neutron