1. Quantum Mechanics: What are the electron energies?
Bohr Model
Quantum Mechanical Model
(High P.E.) 3d 3p
n=3 3s 2p
n=2 2s
n=1 1s
(Low P.E.)

2. Factors that affect electron energies: Orbital Sizep+ e-
Hydrogen Atom p+
1s orbital e-
Hydrogen Atom
Remove the electron and compare! 1s 2s
High P.E.
Low P.E.
... e- closer to nucleus
...e- further from nucleus
... greater e- ... p+ attraction
... weaker e- ... p+ attraction
... harder to remove e-
... easier to remove e-
... lower energy e-
... higher energy e-

3. Factors that affect electron energies: Additional e-
Neutral Helium Atom
He+ Cation
The first electron removed from an orbital has higher P.E. than the second electron removed from the same orbital.
2p+
1s orbital e-
Remove the electron and compare!
2p+ e-
1s orbital
...electrons are the same distance from nucleus
...1 electron attracted by nucleus
...2 electrons repel each other
...no electron-electron repulsion
... electron easier to remove
... electron harder to remove
... higher energy e-
... lower energy e-