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Glossary of chem ch 5

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Daltons atomic model
the first modern atomic theory to state that elements are composed of minute individual particles called atoms
law of definite composition
a compound always contains two or more elements combined in a definite proportion by mass
law of multiple proportions
atoms of two or more elements may combine in different ratios to produce more than one compound
subatomic particles
particles found within the atom, painly protons, neutrons, and electrons
electron
a particle with a negative electronical charge
proton
a subatomic particle found in the nucleaus of the atom that caries a positive electrical charge
neutron
a subatomic paritcle that is electrically neutral and is found in the nucleus of an atom
Thomson model of the atom
thomson asserted that atoms are not indivisible but are comjposed of smaller parts; they contain both positively and negatively charged particles-protons as well as electrons
nucleus
the central part of an atom that contains all its protons and neutrons, its very dense andhas a positive electrical charge
atomic number
the number of protons in the nucleus of an atom of that element
isotopes
atoms of an element having the same atomic number but different atomic masses
mass number
the sum of the number of protons and the number of neutrons in the nucleus
atomic mass unit
a unit of mass equal to one-twelfth the mass of carbon-12 atoms
atomic mass
the average relative mass of the isotopes that element compared to the atomic mass or carbon-12
Dalton
revived the concepts of atoms and proposed an atomic model based on facts and experiments evidence
Thomson
discovered the nature of a proton
Rutherford
established that positive charged alpha particles emitted by certain radioactive elements are ions of Helium
ions
a positively or negatively charged atom or group of atoms
cations
positively charged ions
anions
negatively charged ions
cathode rays
the emissions gereated in a Crookes tube
isotopic notation
notation for an isotope of an element where the subscript is the atomic number, the superscript is the mass number, and they are attached on the left of the symbol for the element

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