History of the Atomic ModelHistory of the Atomic Model
How the model of the atom haschanged or evolved over timeHow the model of the atom haschanged or evolved over time
Definition of an AtomDefinition of an Atom
The smallest particleof an elementThe smallest particleof an element
There are 2,000 billionbillion atoms of oxygenin one drop of waterThere are 2,000 billionbillion atoms of oxygenin one drop of water
Atomic StructureAtomic Structure
Atoms are made up of three basicparticlesAtoms are made up of three basicparticles
Protons: Carry a positive chargeProtons: Carry a positive charge
Neutrons: Carry no chargeNeutrons: Carry no charge
Protons and neutrons join together to form thenucleus- the central part of the atomProtons and neutrons join together to form thenucleus- the central part of the atom
Electrons: carry a negative charge and circlearound the nucleusElectrons: carry a negative charge and circlearound the nucleus
Atomic StructureElectronsAtomic StructureElectrons
Electrons travel around the nucleus inenergy shells or orbitals.Electrons travel around the nucleus inenergy shells or orbitals.
Each orbital can only hold a certainamount of electrons.Each orbital can only hold a certainamount of electrons.
Atomic StructureAtomic Structure
Atomic StructureAtomic Structure
Protons and neutrons have the same mass andare the heaviest part of the atomProtons and neutrons have the same mass andare the heaviest part of the atom
Electrons are much smaller, move faster, andgive the atom its volumeElectrons are much smaller, move faster, andgive the atom its volume
How have scientists figured thisout ????How have scientists figured thisout ????
The Greek Model (460-440 BC)The Greek Model (460-440 BC)
Democritus was a Greek philosopherDemocritus was a Greek philosopher
Matter cannot be divided into smallerand smaller pieces forever.Matter cannot be divided into smallerand smaller pieces forever.
The smallest piece called an “atom”The smallest piece called an “atom”
Dalton (1790-1807)Dalton (1790-1807)
Atoms are indivisible and indestructibleAtoms are indivisible and indestructible
Atoms of the same element are exactlyalike, atoms of different elements are notAtoms of the same element are exactlyalike, atoms of different elements are not
Atoms can combine to form more complexcompoundsAtoms can combine to form more complexcompounds
Thomson (1887-1898)Thomson (1887-1898)
Called the “Plum Pudding” ModelCalled the “Plum Pudding” Model
Atoms are divisible.Atoms are divisible.
Discovered negatively charged particles,called electrons.Discovered negatively charged particles,called electrons.
Believed atom was like a positivepudding with negative electrons stuck init.Believed atom was like a positivepudding with negative electrons stuck init.
Rutherford (1909-1919)Rutherford (1909-1919)
Conducted the Gold Foil ExperimentConducted the Gold Foil Experiment
Found that atom was mostly empty spacewith very dense, positive centerFound that atom was mostly empty spacewith very dense, positive center
Electrons on the edge of the atom.Electrons on the edge of the atom.
Bohr (1913 - 1920)Bohr (1913 - 1920)
Found that electrons did not moverandomly around nucleus, they haddefinite paths or “orbits”Found that electrons did not moverandomly around nucleus, they haddefinite paths or “orbits”
Each orbit only holds a certain number ofelectronsEach orbit only holds a certain number ofelectrons
Electrons can jump from one orbit toanother (quantum jump)Electrons can jump from one orbit toanother (quantum jump)
Electron Cloud Model (current)Electron Cloud Model (current)
Dense nucleus is surrounded by a cloudwhere the electrons areDense nucleus is surrounded by a cloudwhere the electrons are
The cloud has energy levels.The cloud has energy levels.
Electrons may “jump” back and forthbetween energy levels.Electrons may “jump” back and forthbetween energy levels.
Whose model is represented by thepictures?Whose model is represented by thepictures?
Whose model is represented by thepictures?Whose model is represented by thepictures?