| A | B |
|---|
| Atom | smallest part of matter |
| Atomos | Greek for "not to be cut" or "indivisible" |
| Model | picture which uses familiar ideas to explain unfamiliar facts in nature |
| Greek ( Democritus) | i. atom is smallest part of matter ii. small hard particles which are indivisible iii. infinite, always moving and capable of joining iv. made of same material, but different shapes and sizes |
| Dalton | i. all elements are composed of atoms, which are indivisible and indestructible ii. atoms of the same element are exactly alike; atoms of the same element are exactly alike; atoms are different elements are different iii. compounds are formed by the joining of atoms of two or more elements |
| Thomson | i. plum-pudding model ii. atom was made of puddlinglike positively charged material throughout which negatively charged electrons were scattered like raisins in a pudding. |
| Rutherford | i. all of an atom's positively charged particles were contained in the nucleus ii. negatively charged electrons were scattered outside the nucleus around the atom's edge. |
| Bohr | i. electrons move in definite orbits around the nucleus, much like planets circles the sun ii. the orbits, or energy levels, are located at certain distances from the nucleus |
| Wave (quantum) | i. based on principle of wave mechanics ii. electrons do not move about an atom in definite paths like planets around the sun iii. impossible to determine the exact location of an electron iv. scientists can only predict where an electron is most likely to be found v. and atom has a small positively charged nucleus surrounded by a large region in which there are enough electrons to make the atom neutral |
| Subatomic Particles | parts of an atom |
| Nucleus (parts of an atom) | small, dense positively charged center of an atom |
| Proton (parts of an atom) | positively charged subatomic particle located in the nucleus of the atom |
| Neutron (parts of an atom) | neutral subatomic particle located in the nucleus of an atom |
| Electron (parts of an atom) | negatively charged particle found in area of atom outside of nucleus |
| Electron Cloud | space in which electrons are likely to be found |
| Energy Levels | most likely location in an electron cloud in which an electron can be found |
| Quark | sub-subatomic particle located in protons and neutrons |
| Atomic Number | the number of protons in the nucleus of an atom; identifies the element |
| Mass number | the sum of the protons and neutrons in the nucleus |
| Atomic mass | average mass of all the isotopes of an element as they occur in nature |
| Atomic mass unit | unit of mass of subatomic particles; one proton is equal to one AMU |
| Isotopes | atom that has the same number of protons as another atom, but a different number of neutrons |
| Four forces | forces that account for the behavior of subatomic particles |
| Electromagnetic force | force of attraction between charged particles |
| Strong force (nuclear) | strongest of the four forces; opposes electromagnetic force |
| Weak force | responsible for radioactive decay |
| Gravity | weakest force in nature; force of attraction between all objects in the universe |
