Electron configurations
10/23/12
What is an electron configuration?
• The ways in which the atoms are arranged in
orbitals around the nucleus of an atom.
What is an atomic orbital?
• A region of space where an electron is likely to
be found.
orbital
Describe the shape Draw a picture of the shape
Write the number of
orbitals at each energy
level
s
Round, like a ball
p
d
f
Two raindrops
connected
1-4 = clover leaf
shape
5= raindrops with
a ring around the
middle
8 regions in
different planes
1
3
5
7
What are the rules for filling orbital
diagrams
• Aufbau Principle: Electrons fill lowest energy
levels first.
• Pauli Exclusion Principle: Each orbital can have
2 electrons. They must have opposite spin.
• Hund’s Rule: Electrons will fill in the same
energy level, so that the number of electrons
with the same spin is as great as possible.
How do you complete an orbital filling
diagram?
How do you write out an electron
configuration?
• Standard method: 1s2 2s2 2p6 3s2 3p6 4s1
• Short hand method: [Ar] 4s1
What are Valence Electrons?
• Electrons in the highest occupied energy level
of an atom.
• These are the electrons that largely determine
the
What is the octet rule?
• In forming bonds or reacting with other
elements, an atom will usually try to have 8
valence electrons.