Amador Valley HS Chemistry
STUDENT Notes: Quantum Numbers
Name: E. Schnell
Date: Yearly
Period: Chemistry
Remember from our discussion on visible LIGHT, that when an electron is EXCITED by an outside input of
ENERGY it can absorb only a quantum (amount) of energy needed to jump to one of the higher energy levels.
When it spontaneously falls back down to a LOWER energy level, the electron emits a quantum of ENERGY
equal to the difference between the two energy levels. If the wavelength of that energy emitted falls into the range
of VISIBLE light, we will see a certain color corresponding to that wavelength.
Hydrogen’s emission SPECTRUM helped scientists begin to formulate this idea of Quantum numbers and relate it
to an electron’s location within an ATOM.
Your home address is your most probable location, even though you are not there all the time. Your address is
made up of four parts: STREET, city, street, and house number. The four quantum numbers, n, l, m, and s can be
thought of as the address for an electron in an atom.
The principal quantum number, n, describes the energy level or average distance the electron is from the
NUCLEUS. It may be helpful to think of it as the size of the energy level with n=1 being SMALLER and having
less energy that n=5 for example. Although n can have integer values from 1 to , seven is the highest energy level
we will use. In other words, there can be seven states, if we use our address analogy.
The second quantum number, l, describes the sublevels within the energy level. A CITY is a sublevel of the state.
Just as there are small states having fewer cities than large states, so the energy levels have different numbers of
SUBLEVELS. The first energy level, n = 1, is so small that there is only one sublevel. The fourth energy level is
larger and has four SUBLEVELS. Using our analogy, the fourth energy level or state has four different sublevels
or cities. The sublevels are named s, p, d, f.
Energy level
n=1
n=2
n=3
n=4
up to
n=
Sublevel
s
s, p
s, p, d
s, p, d, f
s, p, d, f
The third Quantum number is the magnetic quantum number, m. Each sublevel (s, p, d, f) contains one or more
orbitals. The space occupied by one pair of electrons is called an ORBITAL. In our address analogy, the orbitals
are like streets within a city. Just as streets are oriented north-south or EAST - WEST, orbitals are oriented in a
magnetic field about the x, y, and z-axes.
The s sublevel contains only one orbital. The p sublevel contains 3 orbitals arranged along the three perpendicular
x, y, and z-axes. The d sublevel is made up of 5 orbitals, while each f sublevel contains 7 orbitals. In our address
analogy, there are seven streets in the f city.
Example: 2 p x
____2___ energy level
Double-lobe shaped _______________
Oriented on the __x__-axis
Two electrons can share these three same quantum numbers.
Sublevel
Shape of orbital
Number of Orbitals and how to draw them
Number of electrons
s
spherical
1
2
p
Double-lobed
3
6
d
complex lobe
5
10
f
more complex lobe
7
14
The 4th quantum number is the s or SPIN quantum number. It describes the clockwise or counter-clockwise
rotation of the ELECTRON. We can also think of these as spin-up vs. spin-down or +1/2 vs. -1/2.
Each orbital can have 2 values for spin. These values represent the pair of electrons that can occupy a single orbital.
Using the address analogy again, the spin value represents the house number.
As in the address analogy, each quantum numbers provides more specific information on the probable location of
an electron.
Here’s an example of the “address” for one electron: 2 p x (+1/2)
2nd Energy Level
Double-lobe shaped orbital
Oriented on the x-axis
____+1/2_____ spin
Only ONE electron can have these same ADDRESS.
What would be the address of the other electron in the same orbital?
Whew! With that being said, let’s put our newly found knowledge of electron location to practice.
We are now going to draw ELECTON ORBITAL DIAGRAMS for specific ELEMENTS found on the
periodic table.
Orbitals are not all-equal energy so we must first figure out in what order they fill. With a few exceptions, the
ORBITALS will fill according to INCREASING energy. The Chemistry textbook has the proper filling order
chart on page 138.
Hydrogen
Orbital diagram
Electron configuration
1s1
E.C.
using noble gas notation
None
Helium
Orbital diagram
Electron configuration
1s2
E.C.
using noble gas notation
None
Lithium
Orbital diagram
Electron configuration
1s22s1
E.C.
using noble gas notation
[He]2s1
Carbon
Orbital diagram
Electron configuration
1s22s22p2
E.C.
using noble gas notation
[He]2s22p2
Neon
Orbital diagram
Electron configuration
1s22s22p6
E.C.
using noble gas notation
[He] 2s22p6
Magnesium
Orbital diagram
Electron configuration
1s22s22p63s2
E.C.
using noble gas notation
[Ne]3s2
Chlorine
Orb3dital diagram
Electron configuration
1s22s22p63s23p5
E.C.
using noble gas notation
[Ne] 3s23p5
Potassium
Orbital diagram
Electron configuration
1s22s22p63s23p64s1
E.C.
using noble gas notation
[Ar] 4s1
Iron
Orbital diagram
Electron configuration
1s22s22p63s23p64s23d6
E.C.
using noble gas notation
[Ar] 4s23d6
Krypton
Orbital diagram
Electron configuration
1s22s22p63s23p64s23d104p6
E.C.
using noble gas notation
[Ar] 4s23d104p6
Gold
Orbital diagram
Electron configuration
1s22s22p63s23p64s23d104p65s24d105p66s14f145d10 - Exception
E.C.
using noble gas notation
[Xe] 6s14f145d10 - Exception