Genchem CH 2 - The nuclear model of the atom - Chemistry: a Molecular Approach PDF

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The nuclear model of the atom...

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Chapter 2: The Nuclear Model of the Atom - IMPORTANT - Properties => # electrons - Atoms of element: same # electrons - Atoms: Neutral, + and – cancel - protons = electrons - All of element: same # protons - Neutrons: neutral - # neutrons can ≠ electrons - Atoms of element: unequal neutrons, Isotopes Symbols of Elements - Num. of protons: atomic number, Z - Mass number: protons  plus neutrons - NB: Z often not written - Num. Protons define element - Num. Neutrons => Mass Number -

Ions -

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Num. Electrons => neutral / ion Neutral atoms => gain/lose e- => net charge (+ or -): ION - Cation: e- (s) lost (+) - Anions: e- (s) gained (-)  Notation - Cations: 1 H+ (or just H+ ) - Anions: 16 O2- (or just O2- )

Isotopes - Same element, ≠ masses (neutrons)

Periodic Table

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Atomic Weight of Elements ATOMIC MASS => individual atom -

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units (AMU) (~ mass of proton) ≠ Mass Number 1 amu = 1.66 x 10-24  g Each isotope: own atomic mass, ~ Mass Number Mass spectrometers

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