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Chem Chapter 4
Term | Definition |
---|---|
Democritus | ________ (460–370 B.C.E.) and his mentor Leucippus (fifth century B.C.E.) recorded ideas of atoms. |
Dalton | In 1808—over 2000 years later—_____ formalized a theory of atoms that gained broad acceptance. |
Thomson | An English physicist named ______ (1856–1940) discovered a smaller and more fundamental particle called the electron. |
Rutherford | _________'s gold foil experiment (1909): Tiny particles called alpha-particles were directed at a thin sheet of gold foil. |
Repel | Positive–positive and negative–negative charges ____ each other. |
Attract | Positive and negative electrical charges ______ each other. |
Atomic Number | The number of protons in the nucleus of an atom is its ____ ______ and is given the symbol Z. |
Dmitri Mendeleev | ____ ____ , a Russian chemistry professor, proposed from observation that when the elements are arranged in order of increasing relative mass, certain sets of properties recur periodically. |
Metals | occupy the left side of the periodic table and have similar properties |
Nonmetals | occupy the upper right side of the periodic table |
Metalloids | lie along the zigzag diagonal line dividing metals and nonmetals. |
Semiconductors | Metalloids are also called ________ because of their intermediate electrical conductivity, which can be changed and controlled. |
Ions | In chemical reactions, atoms often lose or gain electrons to form charged particles called ___ |
Cation | Positive Ions |
Anion | Negative Ions |
Isotopes | Atoms with the same number of protons but different numbers of neutrons are called _______ |
Natural Abundance | All elements have their own unique percent _____ ________ of isotopes. |
Neutrons | The number of ________ in an isotope is the difference between the mass number and the atomic number. |
Nuclear Radiation | The emitted subatomic particles are called ____ _______ |
Radioactive | The isotopes that emit them are termed ________ |