14 terms

Prentice Hall Chemistry Chapter 4

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atom
the smallest particle of an element that retains its identity in a chemical formula
Democritus
believed that atoms were indivisible and and indestructible
Dalton
Atomic Theory - Atoms of the same element are identical. atoms can be combined into whole number ratios
electrons
negatively charged, floating around nucleus. number is the same as protons
protons
positively charged. inside the nucleus, same number as atomic number
neutrons
no charge, inside nucleus. atomic mass - proton = # of neutrons
nucleus
tiny central core of an atom composed of protons and neutrons. positively charged
Rutherford
gold foil experiment - atoms are made up if mostly empty space with a small dense nucleus in the center
Thomson
cathode ray, discovered that electrons have a negative charge.
Bohr
proposed that an electron is found only in orbits, around nucleus
period
the horizontal rows on a periodic table
group
each vertical column of the periodic table
atomic mass unit
(AMU) unit used when finding relative abundance
Isotopes
atoms that have the same number of protons but different number of neutrons