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13 terms

Ch. 4 Introduction to Atoms

vocab
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atom
the smallest particle into which an element can be divided and still be the same substance
theory
a unifying explanation for a broad range of hypotheses and observations that have been supported by testing
electrons
the negatively charged particles found in all atoms
model
a representation of an object or system
nucleus
the tiny, extremely dense, positively charged region in the center of an atom
electron clouds
the regions inside an atom where electrons are likely to be found
protons
the positively charged particles of the nucleus
atomic mass unit
the SI unit used to express the masses of particles in atoms
neutrons
the particles of the nucleus that have no charge
atomic number
the number of protons in the nucleus of an atom
isotopes
atoms that have the same number of protons but have different numbers of neutrons
mass number
the sum of the protons and neutrons in an atom
atomic mass
the weighted average of the masses of all the naturally occurring isotopes of an element