Download o Positive charge • Electrons

Chemistry 1A
Week 1
Lecture Notes
Atom
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Nucleus
o Protons (+), neutrons (o)
o Positive charge
Electrons (-)
Subatomic particles (protons, neutrons, electrons)
o Measured in atomic mass units (u)
o Neutral atom: protons = electrons
Overall mass made of protons + neutrons (mass of electrons is insignificant)
Overall volume/size made of protons, neutrons & electrons
Molecule
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Collection of atoms chemically bonded & uncharged
Element
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Collection of one type of atom
Defined by number of protons
Represented by chemical symbol:
Where A = Mass No, Z = Atomic No, C+/- = charge
Ion
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Atoms that have gained or lost electrons
Gained electrons: Charge is negative (anion)
Lost electrons: Charge is positive (cation)
Isotope
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Atom with different number of protons and neutrons
Heavier isotopes occur in natural abundances
Atomic mass (u) = average mass of atoms of isotopes as the occur naturally
To calculate:
o Divide percentages by 100 to find natural abundances
o Atomic mass = (abundance 1 x mass 1) + (abundance 2 x mass 2)