History Of Atoms Flashcards
Who named the atom
Democritus
What did Democritus say?
Matter cannot be divided forever
What is an atom?
The smallest particle of an element that retains its properties
What did Aristotle think matter was made of?
A combination of earth, wind, fire, and water
Daltons atomic theory?
- Elements composed of atoms; atoms are indestructible
- Atoms of same element are exactly alike
- Atoms of different element are different
- Compounds formed by joining 2 atoms in whole number ratios
What part of Daltons atomic theory was wrong
Atoms of the same element are the same (they are not, isotopes exist)
J.J Thompson’s experiment?
Passed electricity through an uncharged gas and saw the gas turned negative, concluded the atoms had negative particles in them
After finding out about electrons, what did Thompson conclude about atoms?
They also had a positive charge because they were usually neutral
Thompson’s model?
Plum Pudding model, atom is made of positive with electrons scattered in there like raisins in pudding
Rutherford experiment?
Shot positive particles through gold foil, saw most atoms passed through
What did Rutherford conclude from his experiment?
Atoms are mostly empty space, but due to the ones that bounced away, the nucleus must be positive
What did Rutherford name the center of the atom?
Nucleus
What was new in Bohr’s model?
Electrons moving in energy levels in fixed orbit around the nucleus
What was wrong about Bohr’s model?
The electrons being in fixed orbits; they actually don’t move in a fixed path
According to the theory of wave mechanics…
Electrons do not have a fixed orbit
Can you determine exactly where an electron is in an atom?
No; you can only get a probable location from the energy of the electron
The most modern model of atoms has
The electron cloud where electrons whirl around billions of times per second
Who hypothesized the existence of neutrons, but couldn’t prove it?
Rutherford
Who proved that neutrons were real?
James Chadwick in 1932
What did Democritus theorize about the properties of atoms?
they are small and hard, differ in shape and size, infinite, always moving, and capable of joining.
What parts of Democritus’ theory were wrong?
Atoms are not hard or infinite in number
