ATOMIC THEORYThe development of our knowledge of Chemistry

Democritus A greek Philosopher who , in about 300

BCE suggested that the stuff around us ( matter) is composed of very small little particles.

He called them “Atomos”

The detractors:Most scientists of the day, thought Democritus must have been…Smoking crack or something!They all “knew” that matter was made up of the four elements:Earth, Wind, Fire, and Water!!!!

John Dalton In the Late 1700’s to early 1800’s John

Dalton suggested to the world that: Matter is composed of small little

particles …. Called “atoms” He is known as the Father of Modern

Chemistry He did some experimentation to help him

come up with the 4 principles of matter….

1. All elements are made up of small indivisible particles called “atoms”

2. Atoms of one element are “identical” but atoms of other elements are different from the others. ( all Au atoms are “the same” all Al atoms are “the same” but Al and Au are different)

3. Atoms can combine in small whole number ratios to form compounds

4. Atoms can be rearranged, and recombined when they form compounds, but they are never changed.

The detractors…. A great many “scientists” and

philosophers thought Dalton must have been….

Smoking crack or something!!!!!

Because they all knew that matter was composed of Earth, Wind, Fire, and Water!!!!!

Dimitri Mendeleev By the mid 1800’s there were about 70

elements known. Mendeleev came up with a way to

organize them, based on their atomic mass.

He essentially created the 1st periodic table

JJ Thomson In 1897 JJ Thomson used a cathode ray

tube that looked kinda like this…..

And discovered the electron!!!!! Other scientists working to study the atom

determined that the electron must have a mass of about 9.1 x 10-28 g

current value: 9.109 x 10-28g!

Neils BohrIn about 1913, Neils Bohr came up with the idea that electrons revolve around the atom in orbits around the atom. Similar to the way planets orbit a star

We now know that this Is not exactly how it is!

Ernest Rutherford In early 1900’s (1920) or so, Ernest

Rutherford did an experiment famously know as the “Gold Foil Experiment”

It looked like this…..

His experiment showed that there was something in the atom that:

Had mass Had a positive charge It was the proton!!!!

The atom is mostly empty space! If I found a good visual to cut and

paste…. If not……

James Chadwick In about 1930, James Chadwick did some

experiments similar to JJ Thomson. He used a cathode ray tube and…. Discovered the Neutron!

Summer 2012 The Higgs Boson was discovered? Postulated in about 1965 or so, The Higgs

Boson is some magical and mythical “thingy” that helps give matter its mass.

Some, including scientists, refer to it as “The God Particle!” as it will perhaps help us understand matter a little bit better

A few days Later, Mr. Jury still doesn’t understand what the

Higgs Boson is all about

What problems/ obstacles did the scientists have when they were trying to figure out what “stuff’ ( matter) was made of?

What technological barriers did they face?

What do doctors need to do when they are trying to help cure a sick patient?

Are doctors always successful? Explain!