atoms
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Greek Atomic Greek Atomic ModelModel
•Democritus (400 BC)Democritus (400 BC)•Named the atomNamed the atom•Atom cannot be Atom cannot be divideddivided
Dalton’s Dalton’s AtomicAtomic Theory Theory•18031803
•All elements are composed All elements are composed of atoms (not divisible)of atoms (not divisible)
•Atoms of same element are Atoms of same element are the samethe same
•Atoms of different Atoms of different elements are differentelements are different
Thomson’s Thomson’s ModelModel
•18971897•Atom has smaller parts, Atom has smaller parts, like electronslike electrons
•Atom made of a positive Atom made of a positive pudding-like material with pudding-like material with negatively charged negatively charged electrons scattered electrons scattered throughoutthroughout
Rutherford’s Rutherford’s ModelModel
•19111911•Positive-charged Positive-charged particles in the nucleusparticles in the nucleus
•Negative scattered Negative scattered around edgesaround edges
•Gold foil experimentGold foil experiment
Bohr’s Bohr’s ModelModel
•19131913•Electrons move in definite Electrons move in definite orbits around the nucleus orbits around the nucleus (like the planets move (like the planets move around the sun)around the sun)
•Energy levels located a Energy levels located a certain distance from the certain distance from the nucleusnucleus
Wave Wave TheoryTheory
•Modern modelModern model•Electrons do not travel Electrons do not travel in definite pathsin definite paths
•Think electron cloudThink electron cloud
Subatomic Subatomic ParticlesParticles
• protons = positive charge (+)protons = positive charge (+)• electrons = negative charge (-)electrons = negative charge (-)• neutrons = neutral (0 charge)neutrons = neutral (0 charge)
Lithium AtomLithium Atom
•How many How many protons?protons?
•How many How many electrons?electrons?
•How many How many neutrons?neutrons?
Atomic NumberAtomic Number
• identifies the element on the identifies the element on the periodic tableperiodic table
• equals the # of protons in the equals the # of protons in the nucleusnucleus
Atomic MassAtomic Mass
• sum of the # of protons + # of sum of the # of protons + # of neutrons in the nucleusneutrons in the nucleus
• changes with isotopeschanges with isotopes
IsotopesIsotopes• atoms of the same elementatoms of the same element• same # of protonssame # of protons• different # of neutronsdifferent # of neutrons• different atomic mass different atomic mass • examples = hydrogen, carbon, examples = hydrogen, carbon,
uraniumuranium
Electron Electron CloudCloud• electrons move electrons move
about the about the nucleus locked nucleus locked in a certain in a certain area of the area of the electron cloudelectron cloud
• location called location called energy levelsenergy levels
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