MR. SURRETTE
VAN NUYS HIGH SCHOOL
CHAPTER 14: MODERN ELECTRON ORBITALS
CLASS NOTES
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. 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. 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. 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.” 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. Conversely, if this same electron “falls back” to the n = 1
level, it loses energy in the form of photons.
SHELLS AND SUBSHELLS
The principal quantum number (shell) determines the number of subshells that electrons can occupy.
SHELLS AND SUBSHELLS TABLE
Shell
n=1
n=2
n=3
n=4
# of
subshells
1
2
3
4
Subshells
l=s
l = s, p
l = s, p, d
l = s, p, d, f
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.
CHEMISTRY
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MR. SURRETTE
VAN NUYS HIGH SCHOOL
SUBSHELLS AND ELECTRONS TABLE
Subshell
l= s
l=p
l=d
l=f
# of
orbitals
1
3
5
7
Max # of
electrons
2 e6 e10 e14 e-
THE s SUBSHELL
The spherical s subshell surrounds the nucleus in all directions:
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
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. Elements are listed on the periodic table from left to right, top to
bottom, by order of their atomic number.
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.
FIRST ENERGY LEVEL
The shell closest to the nucleus (n = 1) contains the least amount of energy. This shell only contains one
orbital, the 1s. As a result, the first energy level (n = 1) holds two electrons.
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MR. SURRETTE
VAN NUYS HIGH SCHOOL
SECOND 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. Since each subshell holds two electrons, the second energy level (n = 2) holds
eight electrons.
THIRD ENERGY LEVEL
The third energy shell (n = 3) also contains one s subshell and three p subshells. These are the 3s and 3p
orbitals. The third energy level (n = 3) holds eight electrons.
ENERGY LEVELS FOUR – SEVEN
The higher energy shells (n = 4, 5, 6, and 7) contain s, p, d, and f subshells. The d and f subshells
produce the transition metals (so named because their electrons are free to transition between energy
levels). The five d subshells can hold ten electrons and the seven f subshells can hold fourteen
electrons.
ENERGY LEVELS AND ORBITALS TABLE
(n = 1): 1s
(n = 2): 2s, 2p
(n = 3): 3s, 3d, 3p
(n = 4): 4s, 4d, 4p
(n = 5): 5s, 5d, 5p
(n = 6): 6s, 6f, 6d, 6p
(n = 7): 7s, 7f, 7d, 7p
THE PERIODIC TABLE AND ENERGY LEVELS
The first row of elements in the periodic table (hydrogen and helium) contain n = 1 electrons. The
second row of elements contain n = 1 and n = 2 electrons (the n = 2 electrons are outside the n = 1
electrons). The third row of elements contain n = 1, n = 2, and n = 3 electrons. This progression of
energy levels continues for the rest of the periodic table.
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