Flashcards

History of the Atom

Jade Dickey English 14 cards

Cards in this deck (14)

1Atoms...Are the smallest particles into which an element can be divided and will remain the same substance
...Make up elements (which combine to form compounds)
...often called the building blocks of matter
2Atoms... Pt. 2...Were not seen prior to 1981 when the scanning tunneling microscope was invented
...comes from the Greek word atomos, meaning indivisible
However...
The atomic theory has been around for more than 2000 years!
3TheoryA theory is an explanation for a broad range of hypotheses and observations that have been supported by testing
4Democritus proposed (around 440 BC)......that if a person continued to cut a coin in half over and over again, they would eventually end up with an uncuttable piece
...
the name for the atom
5Aristotle disagrees. He thought (around mid 300 BC, after Democritus)...particles could be divided indefinitely
6about 2000 years have passed. What are combined elements with a constant mass ration called?...in the 1700’s, scientists have learned that elements combine in specific proportions based on mass
What are combined elements with a constant mass ration called?
Compounds!
7Dalton’s Theory Stated...All substances are made of atoms. Atoms are small particles that cannot be created, divided, or destroyed
Atoms of the same element are exactly alike, and atoms of different elements are different
Atoms join with other atoms to make new substances
8So, is the atom really the smallest particle ?We thought so until 1897 (yes, just 110 years ago!) Another British scientist, J.J.Thomson, discovered that there were small particles inside the atom, therefore, the atom could be divided into smaller parts!
9Thompson experimented with the cathode ray tube and discovered...the discovery of the electron!
He is known for the “plum pudding” or “chocolate chip cookie” model of the atom.
10A Few Years Later...
A student of Thompson’s named Ernest Rutherford decided to check out Thompson’s theory himself so he set up an atomic shooting gallery
Rutherford came up with his own model of the atom (after his performance of the gold foil experiment)
He is credited with the discovery of the proton and nucleus
Rutherford's model came to be known as the “solar system” model
11Niels BohrNiels Bohr (who worked with Rutherford) suggested that electrons travel around the nucleus in definite paths
Bohr also proposed that the electrons could jump between paths
12Electron Clouds and Current TheoryThe exact movement of an electron cannot be predicted but, according to current theory, there are regions of the atom where the electrons are more likely to be found. These are called electron clouds.
13Chadwick...1932Credited with the discovery of the neutron which is located in the nucleus with the protons
14History of the periodic table...Mendeleev–created the first periodic table, ordered by increasing atomic mass
Mosley–rearranged the periodic table in order of increasing atomic #, this is the way the current table is arranged