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Smallest unit of a substance
substances consisting of a single kind of atom
ex. oxygen, gold, iron
a substance formed by a combination of 2 or more elements bonded together
2 or more atoms bounded together
Conservation of mass
the total weight of substances remains constant during a chemical reaction
Law of definite composition
In a compound the mass fraction of each element is always the same
Ex. water always contains 88.8% oxygen and 11.2% hydrogen by mass
Law of multiple proportions
ratio of elements in a compound.
Expressed as 2 or more elements to other are in a ratio of small whole numbers when 2 or more compounds are formed
Atomic theory discovered by...
Atomic theory 4 parts:
1. Matter is composed of atoms that cannot be created or destroyed
2. Atoms of one element can not be converted in atoms of another element
3. Atoms of an element are identical in mass and other properties but add different but add different from atoms of any other element (This meants that atoms of one element weigh more than the atoms of another element)
4. Compounds result in from the chemical combination of a specific ratio of different elements
what does the atomic number equal?
equals the # of protons in the nucleus
# of protons equals
the # of electrons and the atomic #
Isotopes have different numbers of...
number of protons
the # of PROTONS + # of NEUTRONS
atomic mass is also called....
mass spectrometer measures
relative abundance of different isotopes of an element is measured using an intrument
Average atomic weight equals:
the sum of isotope mass times abundance of isotope fro all naturally occurring isotopes