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Atomic Structure

Chapter 4
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atom
Is the smallest particle of an element that retains its identity in a chemical reaction.
atomic mass
the weight average of the masses of the isotopes of an element
atomic mass unit
a unit of mass equal to one-twelfth the mass of a carbon-12 atom
atomic number
the number of protons in the nucleus of an atom of an element
cathode ray
a stream of electrons produced at the negative electrode of a tube containing a gas at low pressure.
Dalton's atomic theory
the first theory to relate chemical changes to events at the atomic level.
electron
a negatively charged subatomic particle
group
a vertical column of elements in the periodic table; the constituent elements of a group have similar chemical and physical properties
isotopes
atoms of the same element that have the same atomic number but different atomic masses due to a different number of neutrons.
mass number
the total number of protons and neutrons in the nucleus of an atom
neutron
a subatomic particle with no charge and a mass of 1 amu; found in the nucleus of an atom
nucleus
the tiny, dense central portion of an atom, composed of protons and neutrons.
period
a horizontal row of elements in the periodic table
periodic table
an arrangement of elements in which the elements are separated into groups bases on a set of repeating properties
proton
a positively charged subatomic particle found in the nucleus of an atom