| Term | Definition |
| was a Greek philosopher | Democritus was |
| proposed the existence of atom | Democritus did |
| thought that matter can be subdivided until a single indivisible particle was reached | Democritus did |
| who was an English school teacher | Dalton was |
| who proposed an atomic model in the early 1800's | Dalton did |
| Who thought that atoms of the same atoms were identical | Dalton did |
| thought that atoms of different elements were different | Dalton did |
| thought compounds formed when atoms of two or more elements combine | Dalton did |
| plum pudding model | thomason's idea |
| negatively charge electrons embedded in positively charged material | plum pudding model |
| discovered the electron | thomason did |
| discovered that the atom is basically empty space | rutherford did |
| credited with the discovery of the nucleus | rutherford was |
| gold foil experiment | rutherford's experiment |
| used alpha particles to study structure of the atom | rutherford did |
| concluded that the atom was mostly empty space with a dense positively charged nucleus in the center | rutherford did |
| was danish scientist | bohr was |
| proposed that the negative electrons were held in orbit by the positive nucleus | bohr did |
| thought that electrons moved in definite orbits around the nucleus | bohr did |
| solar system model | bohr's model |
| proposed that electrons are located in energy levels | bohr did |
| thought electrons were located at certain distances from the nucleus | bohr did |
| wave model | modern atomic model |
| wave model | proposes that electrons do not move in definite orbits |
| wave model | impossible to determine exact electron location |
| wave model | location of electron depends on the amount of energy the electron possesses |
| proton | is a positively charged subatomic particle |
| protons | are located in the nucleus |
| a proton | is slightly smaller in mass than the neutron |
| neutron | is the largest subatomic particle |
| an electron | is negatively charged subatomic particle |
| an electron | is the smallest subatomic particle |
| an electron | are found in "energy cloud" |
| atomic number | determines the identity of atom |
| isotopes | atoms of same element that "weigh" differently |
| isotopes | are atoms of the same element that differ in the number of neutrons |
| mass number | number of particles in the nucleus of an atom |
| mass number | is the number of protons + number of neutrons |
| an electron clouds | is the space around the nucleus where electrons are found |
| two electrons | is the maximum number of electrons in the first energy level |
| eight electrons | is the maximum number of electrons in the second energy level |
| eighteen electrons | is the maximum number of electrons in the third energy level |
| thirty two electrons | maximum number of electrons in the fourth energy level |
| quark | believed to makeup subatomic particles |
| electromagnetic forces | force acting between charged bodies |
| repulsion | is the force between two like charged bodies |
| attraction | is the force between two unlike charged bodies |
| strong force | is responsible for holding the nucleus together |
| weak force | is responsible for the process known as radioactive decay |
| protons | are positively charged subatomic particle |
| Which subatomic particle is least massive? | electron is |
| Which subatomic particle is most massive? | neutron is |
| Almost all the mass of an atom is located where? | within thenucleus |
| The atomic number of sulfur is 16. How many electrons are there in an atom of sulfur-34? | eighteen |
| Atoms emit energy as light when | electrons move to a lower energy level |
| Which part of Dalton's theory was modified after the discovery of isotopes? | Dalton assumed that all atoms of the same element were identical in all ways. However, they may differ in the number of neutrons present. |
| What did Thomason's experiment prove? | proved that the atoms are made of even smaller particles. |
| What must be true if an atom is electrically neutral? | the atom must contain within itself an equal number of electrons and protons. |
| electron configuration | is the arrangement of electrons in the orbitals of the atom |
| energy levels | are the possible energies that electrons in an atom can have. |
| an electron cloud | is a visual model of the most likely locations for the electrons in an atom. |
| the gain or lose energy may result in ______________. | an electron in an atom can from from one energy level to another |
