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20 Cards in this Set
- Front
- Back
definition of "element"
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a substance that cannot be broken down to other substances by chemical reactions. there are 92 recognised elements occurring in natures
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definition of "compound"
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a substance consisting of two or more different elements combined in a fixed ration.
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definition of "trace elements"
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required by an organism in only minute quantities. examples are iron (Fe) and iodine (I).
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definition of "atom"
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the smallest unit of matter that still retains the properties of an element.
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definition of "subatomic particles"
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the tiny bits of matter that compose an atom
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what are the three main types of subatomic particles?
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neutron, proton, and electron
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definition of "atomic nucleus"
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the center of an atom, where protons and neutrons are packed together tightly in a dense core
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what is a dalton?
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a subatomic unit of measurement
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definiton of "atomic number"
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the number of protons, which is unique to each element and is written as a subscript to the left of the symbol for the element.
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definition of "mass number"
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the sum of protons plus neutrons in the nucleus of an atom. written as a superscript to the left of an element's symbol.
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definition of "atomic mass"
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an approximation of the total mass of an atom
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definition of "isotope"
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the different atomic forms of an element, where some atoms have more neutrons than other atoms of the same element and therefore have greater mass.
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definition of "radioactive isotope"
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an isotope in which the nucleus decays spontaneously, giving off particles and energy.
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definition of "energy"
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the capacity to cause change
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definition of "potential energy"
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the nergy that matter possesses because of its location or structure.
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definition of "valence electrons"
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outer electrons; the outermost electron shell is the valence shell
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definiton of an "orbital"
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the sphere where an electron spends 90% of its time
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definiton of "single bond"
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a pair of shared electrons
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definition of "ion"
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a charaged atom (or molecule)
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definition of "cation"
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when an ion's charge is positive
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