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Transcript of Electron Configuration
Electrons move about a nucleus in an atom.
Electrons don't fly off into space because they are attracted to the positively charged nucleus.
In a neutral atom, the # of protons = # of electrons.
Electrons can move between energy levels (shells).
Atoms have unique line spectra because they have unique electron configurations (arrangements).
EQ: How are electrons arranged in an atom?
"Solar System Model"
are only found in certain orbits (aka shells or energy levels)
can move between levels.
Excited State: electrons are in a higher energy level than normal.
Ground vs. Excited State
What causes an electron to change energy levels?
Atoms absorb energy from the environment, which causes the electrons to move faster.
Faster movement = more kinetic energy.
This extra energy causes the electron to go from the ground state to the excited state.
Eventually the atom releases this energy back into the environment as EMR.
The electrons then return to the ground state.
Visible light spectra provide evidence for the Bohr model
1. Continuous spectrum: All of the colors corresponding to the different wavelengths of light can be seen.
2. Line spectrum: Only certain colors/wavelengths can be seen.
If you create a visible light spectrum for an atom:
You get a line spectrum.
The wavelengths of the lines correspond to the different energy levels.
This is one of the reasons we believe energy levels exist in atoms.
1st level - 2 electrons
2nd level - 8 electrons
3rd level - 18 electrons
4th level - 32 electrons
How does this work?
Atomic orbital: An area (space) around the nucleus where you are likely to find electrons.
There is more space for electrons as you move away from the nucleus.
The outer shells have more orbitals and therefore hold more electrons.
Orbital diagrams help us to visualize electron configurations.
Three rules must be followed when drawing orbital diagrams:
Rule 1: Aufbau Principle
"filling up order"
Lowest energy orbitals are filled 1st
Aufbau diagram shows order.
Rule 2: Pauli Exclusion Principle
Each orbital can hold a maximum of two electrons.
Rule 3: Hund's Rule
For a given sublevel, each orbital is filled with a single electron before pairing.
All single electrons must have the same spin.
The direction of the arrow indicates spin.
Example: Draw an orbital diagram for Na
1. Determine the number of electrons.
Electrons = protons, so 11
2. Refer to aufbau diagram
3. Create diagram
Each energy level has sublevels represented by the letters s, p, & d.
s sublevel: 1 orbital, 2 electrons max
p sublevel: 3 orbitals, 6 electrons max
d sublevel: 5 orbitals, 10 electrons max
Numbers correspond to energy levels.
Each space represents an orbital.
Each orbital can hold two electrons.
Arrows are used to represent electrons.
Ground State: electrons are in lowest energy level possible.
Electrons prefer the ground state.
Electron configuration notation:
Similar to an orbital diagram, but electrons are represented by superscripts on atomic orbitals.