Development of Atomic Models. Things Rutherford’s Atomic Model Could Explain Protons and Neutrons...
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Transcript of Development of Atomic Models. Things Rutherford’s Atomic Model Could Explain Protons and Neutrons...
Electrons in AtomsDevelopment of Atomic Models
Things Rutherford’s Atomic Model Could Explain
Protons and Neutrons composed the atomic nucleus
Electrons move around the nucleus in the same way that planets revolve around the sun
And Things it Couldn’tThe chemical properties of elements:
Why do metals give off specific colors when heated?
He needed to better describe the behavior of electrons!
Rutherford’s Model Changed!1913 – The Bohr Model
Energy of an atom changes when it absorbs or emits light
Electrons are only found in specific circular paths, or orbits around the nucleus Each possible orbit have fixed energy levels
Can an electron move into different energy levels?
To move from one energy level to another, they need to gain or lose the right amount of energy
A quantum of energy is the amount of energy required to move an electron from on energy level to another
Another Atomic Model is Developed
1926Schrodinger (Used Mathematical Solutions)Quantum Mechanical Model – determines
the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus
Where can you find electrons?Atomic Orbitals – region in space in which
there is a high probability of finding an electronPrinciple energy levels (n = 1)Energy sublevels (1)
Maximum numbers of electronsEnergy level n # of electrons
1 2
2 8
3 18
4 32
SublevelsSublevel corresponds to a different shaped
orbital
Change Proceeds to Lowest EnergyIn an atom, electrons make the most stable
arrangementElectron Configuration- the ways in which
electrons are arranged in various orbitals around the nucleus of an atom
Aufbau PrincipleElectrons occupy the lowest energy orbital
first
Pauli Exclusion PrincipleAn atomic orbital may describe at most 2
electrons
Hund’s RuleElectrons occupy orbitals of the same energy
in a way that makes the number of electrons with the same spin direction as large as possible
Energy Levels, Sublevels and OrbitalsA sublevel is a region IN the energy level4 possible sublevelsOrbital is a region in the sublevel. Each
orbital can hold only 2 electrons
S 1 orbital 2 electrons
p 3 orbitals 6 electrons
d 5 orbitals 10 electrons
f 7 orbitals 14 electrons
What is light?Newton believed it was made up of particles
BUT it was proven to consist of waves.Wave cycles start at zero, increase to the
highest value, passes through zero to reach its lowest value, and returns to zero again.
3 Properties of WavesAmplitude – the wave’s height from zero to
the crest (highest point of the wave)
Wavelength – distance between the crests
Frequency – the number of wave cycles to pass a given point per unit of time
Calculate Wavelengthλ= c/ν
λ= Wavelength (m)C= Speed of Light (2.998 x108 m/s)
ν= Frequency (/s)
Electromagnetic Spectrum
Practice!Calculate the wavelength of the yellow light
emitted by a sodium lamp. The frequency of the radiation is 5.10x1014 /s.
What is the frequency of radiation with a wavelength of 5.00x10-8m?
Atomic SpectraWhen atoms absorb energy, electrons move
into higher energy levels. These electrons move into higher energy levels
and lose energy by emitting light and returning to the lower energy levels.
Electron EnergyGround State – Lowest possible energy of an
electronn= 1
When an electron absorbs energy it enters an excited stateN= 2,3,4,5,6 etc.
A quantum of energy in the form of light is emitted when an electron drops to a lower energy levelElectronic Transition
Quantum MechanicsEinstein proposed that light could be
described as quanta of energyLight quanta are known as particles
Classical vs. QuantumClassical Mechanics
Describes the motions of bodies much larger than atoms
Quantum MechanicsDescribes the motions of subatomic particles
and atoms as waves
Heisenberg Uncertainty PrincipleIt is impossible to know exactly both the
velocity and position of a particle at the same time