LEUCIPPUS & DEMOCRITUS

2500 Years ago, there was no electric power no modern equipment.
Using only their brains, what could these thinkers possibly have guessed about atoms?

a) matter is composed of tiny particles called atoms which could not be subdivided or made any smaller
b) atoms were different only in size and shape
c) atoms were in constant motion
d) atoms were able to join with other atoms to form different types of matter


DALTON




Dalton had a lab, and had access to chemicals, but had no ability to "see" atoms. Using chemicals and airtight containers, what did he guess about atoms?

a) matter is composed of tiny particles called atoms
b) atoms of a particular element are alike in size, shape, and weight but differ from atoms of other
elements
c) during chemical changes, atoms of different elements unite forming molecules (compounds)
d) during these chemical changes, atoms themselves do not change, that is, are not broken down
e) when atoms combine, they do so in definite whole number ratios by weight


THOMSON



Thomson discovered that when he hooked up a vacuum tube to a strong battery, that a greenish colored beam would flow from the negative plate in the tube to the positive plate.

What did he guess from these results?

a) since these `rays' could be deflected by magnetic and electrical fields they consisted of electrical charges in motion
b) from the direction of deflection the charge on these particles had to be negative
c) these were high velocity particles he called electrons


RUTHERFORD



Rutherford had a radioactive sample that emitted positive particles. He shot these positive particles at a very thin gold foil. 99.999% of these particles passed right through the foil, but .001% got bounced in some unexpected direction.

What did Rutherford guess from this result?


1) positively charged protons concentrated in region inside atom called the nucleus
2) atoms total diameter much larger than that of the nucleus
3) negatively charged particles, called electrons, were circling in orbit around the nucleus
4) a particle in the nucleus having no electrical charge was predicted


CHADWICK




Chadwick shot the same particles that Rutherford used at a piece of Beryllium. Behind this he placed a piece of wax. Coming through the wax, he detected protons being emitted. These were lighter than the original particles, but still just as positive.


What did he realize from the protons that were coming out?

a) found the weight of the atom did not work out and thus found the predicted particles in nucleus with no charge called the neutron
b) neutron weighs about the same as a proton
c) neutron has no electrical charge