23 terms

Chapter 14 Atoms

BHS 2010
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Terms in this set (...)

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
electron
the negatively charged particles found in all atoms; are involved in the formation of all chemical bonds
model
a representation of an object or system
nucleus
the tiny, extremely dense positively charged region in the center of an atom; made up of protons and neutrons
electron cloud
the regions inside an atom where electrons are likely to be found
protons
the positively charged particles of the nucleus; the number of which is the atomic number which determines the identity of an element
AMU or Atomic Mass Unit
the SI unit used to express the masses of particles in an atom
neutrons
the uncharged particles of the nucleus
Atomic number
the number of protons in the nucleus of an atom
isotopes
atoms that have the same number of protons but a different number of neutrons
mass number
the sum of protons and neutrons in an atom
atomic mass
the weighted average of the masses of all the naturally occurring isotopes of an element
ion
an atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons; protons ≠ electrons
radioactive
an unstable atom whose nucleus can change its composition
forces
the pushes or pulls between two objects
gravity
force of attraction between objects that is due to their masses
electromagnetic force
that which causes objects that have the same charge to repel each other and objects with opposite charge to attract each other
strong force
the force between the particles of an atomic nucleus that acts to hold the nucleus together and is the strongest known force
weak force
an important force in radioactive atoms; can change a neutron into a proton and an electron in certain unstable atoms
Democritus
lived around 440 BC and proposed the idea of an "uncuttable" particle that he named an "atom"
Niels Bohr
suggested that electrons travel in specific paths around the nucleus, and "jump" from path to path
Erwin Schrodinger and Werner Heisenberg
proposed the "electron cloud" theory; the exact path of a moving electron cannot be predicted