MR. SURRETTE
VAN NUYS HIGH SCHOOL
CHAPTER 18: MODERN ELECTRON ORBITALS
CLASSNOTES
ELECTRON ORBITALS
Unlike the orbits found in the Bohr model of the atom, electrons do not move around the nucleus in
circular paths. Instead, they occupy regions of space (90% of the time) that surround the nucleus.
ELECTRON ORBITALS
These regions of space are called orbitals and have very specific “quantized” energy levels.
PRINCIPAL QUANTUM NUMBER
Electron orbitals are represented by a number and a letter. For example, “1s” is an orbital. The number
in front of an orbital describes the closeness of an electron to the nucleus.
PRINCIPAL QUANTUM NUMBER
This number is called the principal quantum number.
SHELLS
Depending on context, the principal quantum number is called an energy level or shell. Shells (energy
levels) are represented by the letter n. The lower the n value, the closer the shell is to the nucleus.
SHELLS
For example, an electron in the n = 2 shell is closer to the nucleus than an electron in the n = 3 shell.
SUBSHELLS
The letter in an orbital describes the shape of an electron’s motion. There are four types of shapes: s, p,
d, and f. s = “sharp”, p = “principal”, d = “diffused”, and f = “fundamental.”
SUBSHELLS
These letters represent subshells and are symbolized by the letter l.
ORBITAL ENERGIES (re-visited)
Electrons gain energy as the n value increases. For example, if an electron “jumps” from the n = 1 level
to the n = 3 level, it gains energy.
ORBITAL ENERGIES (re-visited)
Conversely, if this same electron “falls back” to the n = 1 level, it loses energy in the form of photons.
GROUND STATE
Unless stated otherwise, all electrons in this chapter are in the ground state. This means they are in
their lowest energy levels, and are as close to the nucleus as possible.
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MR. SURRETTE
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SUBSHELLS AND ELECTRONS
All four subshells (s, p, d, and f) hold a specific number of orbitals around the nucleus. Each orbital
holds two electrons.
SUBSHELLS AND ELECTRONS TABLE
Subshell
l= s
l=p
l=d
l=f
Max # of
orbitals
1
3
5
7
# of
electrons
2 e6 e10 e14 e-
THE s SUBSHELL
The spherical s subshell surrounds the nucleus in all directions.
THE s SUBSHELL DIAGRAM
LOCATION OF s SUBSHELLS
ON PERIODIC TABLE
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THE p SUBSHELL
The three primary p orbitals look like dumb bells. They surround the nucleus in areas of space along the
x, y, and z axes (the z axis flows into and out of the page).
THE p ORBITALS
LOCATION OF p SUBSHELLS
ON PERIODIC TABLE
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MR. SURRETTE
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THE d SUBSHELL
The three long rows of the periodic table, forming the rectangle from group 3 to group 12, are the
transition metals.
THE d SUBSHELL
Each of these three rows reflects the filling of the five d orbitals. More d orbitals are found on row 7 of
the periodic table.
LOCATION OF TRANSITION METALS
LOCATION OF d SUBSHELLS
ON PERIODIC TABLE
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MR. SURRETTE
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THE f SUBSHELL
The lanthanides and actinides are separated from the rest of the periodic table. They are located at the
very bottom.
LOCATION OF LANTHANIDES AND ACTINIDES
THE f SUBSHELL
These two rows of metals each reflect the filling of the seven f orbitals.
LOCATION OF f SUBSHELLS
ON PERIODIC TABLE
ATOMIC NUMBER
An element’s atomic number is defined by its number of protons. For example, the carbon atom,
atomic number 6, has six protons.
ATOMIC NUMBER
Elements are listed on the periodic table from left to right, top to bottom, by order of their atomic
number.
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CHEMISTRY
MR. SURRETTE
VAN NUYS HIGH SCHOOL
ELECTRONS AND ATOMIC NUMBER
Atoms are electrically neutral. This means the overall net charge of any atom is equal to zero.
Therefore, the number of electrons in an atom equals the number of protons.
SHELLS AND SUBSHELLS
At ground state (lowest energy level), the principal quantum numbers (shells) determine the number of
subshells that electrons can occupy.
1st ENERGY LEVEL
The shell closest to the nucleus (n = 1) contains the least amount of energy. This shell only contains one
orbital, the 1s.
2nd ENERGY LEVEL
The second shell (n = 2) contains one s subshell and three p subshells (called px, py, and pz). These are
the 2s and 2p orbitals.
3rd ENERGY LEVEL
The third energy shell (n = 3) contains one 3s orbital, three 3p orbitals, and five 3d orbitals (the 3d
orbital does not appear until row 4 of the periodic table).
4th ENERGY LEVEL
The fourth energy shell (n = 4) contains one 4s orbital, three 4p orbitals, five 4d orbitals, and seven 4f
orbitals (the 4f orbital does not appear until the lanthanide series, which inserts into row 6 of the
periodic table).
5th ENERGY LEVEL
The fifth energy shell (n = 5) contains one 5s orbital, three 5p orbitals, five 5d orbitals, and seven 5f
orbitals.
6th ENERGY LEVEL
The sixth energy shell (n = 6) does not contain any f subshells. It contains one 6s orbital, three 6p
orbitals, and five 6d orbitals.
7th ENERGY LEVEL
The seventh energy shell (n = 7) contains one 7s orbital and three 7p orbitals.
VALENCE ELECTRONS
Electrons found in the outermost energy shells of atoms are valence electrons. All chemical reactions
involve valence electrons.
VALENCE ELECTRONS
Each succeeding row of the periodic table adds a new energy shell. This creates room for more valence
electrons.
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MR. SURRETTE
VAN NUYS HIGH SCHOOL
ELECTRON LOCATIONS
P/T
Row
1
2
3
4
5
n (energy level)
l (subshell)
1
2
3
4
5
1s
(row 1), 2s, 2p
(row 2), 3s, 3p
(row 3), 3d, 4s, 4p
(row 4), 5s, 5p
Valence
electrons
2
8
8
18
18
6
7
6
7
(row 5), 6s, 5d, 4f, 6p
(row 6) 7s, 6d, 5f, 7p
32
32
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