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26 Cards in this Set
- Front
- Back
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many ancient greek philosophers thought that all matter was made of only four elements-fire, water, and __________ |
earth |
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these early scientists were not able to _______ their theories |
test |
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democritus proposed that matter is made of small, indivisible objects called _________ |
atoms |
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he proposed that different types of _________ are made from different types of atoms |
matter |
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John Dalton proposed the ________ theory which was based on careful observations and _______ of chemical reactions |
atomic. measurements |
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Daltons theory states that atoms cannot be divided, _________ or destroyed |
created |
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it also stated that atoms of one _____ are different from atoms of other _________ |
element. elements |
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a __________ is the smallest piece of an element that still represents the element |
atom |
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atoms were first seen by using __________ microscope |
scanning tunneling |
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Thomson discovered that the rays in a _____________ were attracted to a ___________ charged plate, which means that the rays have a _________ charge |
cathode tube. positive. negative |
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Thomson's atomic model stated that an atom is positively charged __________ with __________ throughout it |
sphere. negatively charged electrons |
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Rutherfords student performed an experiment during which they shot ______ particles into a piece of ________ foil |
alpha. gold |
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The results showed that most of the particles traveled through the foil, but some bounced to the _______ and a few bounced straight back |
side |
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Rutherfords resulting atomic model proposed that most of an atom's _________ and __________ charge is concentrated in the center of an atom |
mass. positive |
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the ____________ is the small, positively charged area in the center of the atom |
Nucleus |
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in the nucleus is the ______ which is an atomic particle with one positive charge |
Proton |
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____________ was one of Rutherfords colleagues |
James Chadwick |
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Chadwick discovered the ___________ a neutral particle that exists in the __________ of an atom |
neutron. nucleus |
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the atomic model of ___________ proposed that _________ move in circular orbits, or ________ around the nucleus |
Neils Bohr. electrons. energy levels |
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When energy is added to an atom, electrons move to higher ____________ when energy is released by the electron, it moves back to a lower level |
energy levels |
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the limitation of Bohr's model is that electrons do not actually move in _________ orbits |
circular |
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in modern atomic theory, electrons form a _______ which is an area around the _________ in which an electron is likely to be located |
electron cloud. nucleus |
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an electron cloud is mostly _______ space |
nucleus |
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an electron cloud is mostly ________ space |
empty |
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protons and _________ are made of smaller parts called _________ |
neutrons. quarts |
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there are ________ types of quarks |
six |
