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23 Cards in this Set
- Front
- Back
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Which scientist discovered the electron?
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Thomson
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Which scientist discovered the nucleus?
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Rutherford
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Which scientist said electrons move around atoms in definite paths?
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Bohr
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What did Dalton propose?
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1. all matter is composed of small particles
2. The small particles can not be divided |
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What is the modern theory of atomic structure?
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The electrons exist in a cloud around the nucleus.
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Why do scientists create models?
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1. represent objects too large
2. represent objects too small to be seen 3. models can be changed with new discoveries |
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What is an Atom?
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The smallest particle into which an element can be divided and still be the same substance.
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What is the Atomic Mass Unit? (AMU)
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SI unit to express the masses of the particles in atoms.
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What are protons?
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Positive particles in the nucleus of an atom.
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What are electrons?
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Negative particles outside the nucleus.
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What are neutrons?
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Neutral particles in the nucleus.
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What is the AMU for Protons, neutrons, and electrons?
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Protons = 1
Neutrons = 1 Electrons = no AMU |
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How do the charges of protons and electrons compare?
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+ = -
(equal and opposite) (cancel each other out) |
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What is the Atomic Number?
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The number of protons in the nucleus.
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What are Ions?
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Charged atoms. Unequal numbers of Protons and electrons.
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What is a neutral atom?
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Uncharged atom. Equal numbers of protons and neutrons.
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What is the Atomic Mass?
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The weighted average of all the naturally occuring isotopes of an element.
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What is the Mass Number?
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The total number of protons and neutrons in a single atom.
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What are Isotopes?
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Atoms with the same number of protons but DIFFERENT NUMBER OF NEUTRONS.
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What is Radioactivity?
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The ability of some elements to give off nuclear radiation.
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How are isotopes the same?
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Same number of protons......same chemical and physical properties
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How do we name an isotope?
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element symbol followed by a hyphen and its mass number
ex. C-14 |
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What is the Electromagnetic Force?
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The attraction between protons and electrons (+ to -)
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