Each electron has a set of four numbers, called quantum numbers, that specify it completely; no two electrons in the same atom can have the same four
1. Principal (shell) quantum number – n
Describes the energy level within the atom.
o Energy levels are 1 to 7
o Maximum number of electrons in n is 2 n^2
2. Momentum (subshell) quantum number – l
Describes the sublevel in n
o Sublevels in the atoms of the known elements are s – p – d – f
o Each energy level has n sublevels.
o Sublevels of different energy levels may have overlapping energies.
The momentum quantum number also describes the shape of the orbital.
* Orbitals have shapes that are best described as spherical (l = 0), polar (l = 1), or cloverleaf (l = 2).
* Orbitals even take on more complex shapes as the value of the angular quantum number becomes larger.
3. Magnetic quantum number – m
Describes the orbital within a sublevel
o s has 1 orbital
o p has 3 orbitals
o d has 5 orbitals
o f has 7 orbitals
Orbitals contain 1 or 2 electrons, never more.
m also describes the direction, or orientation in space for the orbital.
4. Spin quantum number – s
This fourth quantum number describes the spin of the electron.
o Electrons in the same orbital must have opposite spins.
o Possible spins are clockwise or counterclockwise.
Rules governing the combinations of quantum numbers:
* Three quantum numbers n, l, and m are integers.
* The principal quantum number (n) cannot be zero.
o n must be 1, 2, 3, etc.
* The angular quantum number (l) can be any integer between 0 and n – 1.
o For n = 3, l can be either 0, 1, or 2.
* The magnetic quantum number (m) can be any integer between -l and +l.
o For l = 2, m can be either -2, -1, 0, +1, or +2.
* The spin quantum number (s) is arbitrarily assigned the numbers +1/2 and -1/2.

An electrons quantum number is a series of 4 numbers.
The first is the [primary energy level, the second is the subshell, the third describes an orbital withing that subshell, and the last number is either +1/2 or-1/2 — this corresponds to the “spin” of the electron.
The first number can be 1-7, for the seven available energy levels of the known elements. (This corresponds directly to the seven rows of ther periodic table. As you move down rows you move up energy levels)
The second number is either 0, 1, 2, or 3. 0 is the s subshell, 1 is the p subshell, 2 is the d subshell, and 3 is the f subshell.
The third number describes orbitals within the subshell. It ranges from the negative to positive versions of the number of the shell in question. For example, if the second number is 2(d subshell), the third number can be -2, -1, 0, 1, 2. (This corresponds to the 5 orbitals found in the d subshell) If the second number is 1, the third number can be -1, 0 or 1 (Corresponding to the 3 orbitals of the p subshell) Remember each orbital holds two electorns.
The last number, no matter what, can be either +1/2 or -1/2 describing the two electrons within each orbital.
You can think of an quantum number as an address to find an electron — it directs you, more and more specifically, to an electrons “location”
Thats about as simple as I can make it.

There are four Quantum numbers.
they describe four factors that describe the energy of the electron. These four factors give a unique energy to any unique electron found in an atom.
The four Quantum numbers are as follows:.
Principle energy level
sub shell energy level
shell shape or orientation
spin of the electron in its orbital
the values of these four numbers can be put into an equation and a unique energy can be calculated for any electron in an atom.
A good article can be found at the web sight: http://www.ux1.eiu.edu/~cfmdr/The%20Quantum%20Model%20Explained.pdf#search='quantum%20number%20explain‘

You’re kidding, right? A simple explanation of Quantum Numbers.
I hope you are taking either Quantum Theory or Physical Chemistry, so here goes.
There are 3 basic types of molecular motion: translation, rotation, and vibration. These are important because they are ways that molecules can store energy.
Translational motion occurs when molecules are in a container, and the kinetic energy of the total mass of molecules contributes to the total internal energy of the sample.
Molecules can rotate, and the transitions between allowed rotational energy levels are responsible for their spectra (individual wavelengths that can be measured).
Molecular bonds can vibrate, which is also a store of energy, and transitions give rise to vibrational spectra (also measurable).
Quantum numbers are the numbers assigned to describe each of the values for this energy.
Schrodinger’s Equation deals with these different forms of energy, and defines the three Quantum Numbers for :
Principal Quantum Number: n = 1,2,3,4,… infinity
Angular Momentum Quantum Number: l = 0,1,2,… n-1
Magnetic Quantum Number: m(subl) = l,l – 1, l – 2,…, – l
In addition, these are also considered Quantum Numbers:
Total Orbital Angular Momentum :
J = j1+ j2, j1 + j2 – 1,…, l j1 – j2 l
Total Angular Momentum:
L = l1 + l2, l1 + l2 – 1,….l l1 – l2 l (No absolute value bars, sorry)
Total Spin:
S = 1/2 + 1/2,1/2 + 1/2 – 1,…1/2 – 1/2
Electron Shell Number: s,p,d,f,…..
Electron Subshell Number: s=1,p=3,d=5,f=7
If you need further help, you may contact me and I will try to help you out. This is a complex subject, but I am considered a pretty good teacher, so i think I can help you.

The Quantum Numbers
name symbol values
Principal Quantum Number n any integer from 1 to infinity
Azimuthal Quantum Number L any integer from 0 to n-1
Magnetic Quantum Number mL any integer from -L to +L
Spin Quantum Number ms +/- 1/2
for the Worksheet
Generating a Table of Atomic Orbitals
Begin with the lowest value of n (n=1). Calculate all allowable values of L (in this case L =0, only). Name the orbital with the number of “n” and the letter which corresponds with “L,” according to the table below:
L-value orbital type
0 s
1 p
2 d
3 f
The orbital referred to above is the 1s orbital.
Orbitals are filled, lowest energy level first. The energy level of the orbital is approximated by adding the n and L values together and ordering the orbitals according to their n+L values. If n+L values are equal, orbitals with lower “n” values are filled first. According to the Pauli Exclusion Principle, no two electrons may have all four quantum numbers the same.
n L mL ms n+L orbital name order filled
1 0 0 +1/2, -1/2 1 1s 1
2 0 0 +1/2, -1/2 2 2s 2
2 1 -1 +1/2, -1/2 3 2px 3
2 1 0 +1/2, -1/2 3 2py 3
2 1 +1 +1/2, -1/2 3 2pz 3
3 0 0 +1/2, -1/2 3 3s 4
3 1 -1 +1/2, -1/2 4 3px 5
3 1 0 +1/2, -1/2 4 3py 5
3 1 +1 +1/2, -1/2 4 3pz 5
3 2 -2 +1/2, -1/2 5 3d 7
3 2 -1 +1/2, -1/2 5 3d 7
3 2 0 +1/2, -1/2 5 3d 7
3 2 +1 +1/2, -1/2 5 3d 7
3 2 +2 +1/2, -1/2 5 3d 7
4 0 0 +1/2, -1/2 4 4s 6
4 1 -1 +1/2, -1/2 5 4px 8
4 1 0 +1/2, -1/2 5 4py 8
4 1 +1 +1/2, -1/2 5 4pz 8
4 2 -2 +1/2, -1/2 6 4d 10
4 2 -1 +1/2, -1/2 6 4d 10
4 2 0 +1/2, -1/2 6 4d 10
4 2 +1 +1/2, -1/2 6 4d 10
4 2 +2 +1/2, -1/2 6 4d 10
4 3 -3 +1/2, -1/2 7 4f
4 3 -2 +1/2, -1/2 7 4f
4 3 -1 +1/2, -1/2 7 4f
4 3 0 +1/2, -1/2 7 4f
4 3 +1 +1/2, -1/2 7 4f
4 3 +2 +1/2, -1/2 7 4f
4 3 +3 +1/2, -1/2 7 4f
5 0 0 +1/2, -1/2 5 5s 9
5 1 -1 +1/2, -1/2 6 5px 11
5 1 0 +1/2, -1/2 6 5py 11
5 1 +1 +1/2, -1/2 6 5pz 11
etc
The sequence of orbitals just generated is
1s 2s 2px 2py 2pz 3s 3px 3py 3pz 4s 3d 3d 3d 3d 3d 4s 4px 4py 4pz 5s 4d 4d 4d 4d 4d 5px 5py 5pz 6s 5d 5d 5d 5d 5d 4f 4f 4f 4f 4f 4f 4f etc.
The fourth quantum number, the spin quantum number, allows two electrons of opposite spin (or symmetry) into each orbital. The electron configurations of several atoms are on the following table.
Some of the shortcuts employed in the table below are
using the symbol for the previous noble gas to represent all of the orbitals in that noble gas.
when the p or d orbitals are completely filled, expressing those as p6 or d10.
atom atomic number electron configuration
H 1 1s1 (meaning one electron in the 1s orbital)
He 2 1s2
Li 3 1s2 2s1 or He 2s1
Be 4 1s2 2s2 or He 2s2
B 5 1s2 2s2 2px1 or He 2s2 2px1
C 6 1s2 2s2 2px1 2py1 or He 2s2 2px1 2py1 (* see Hund’s Rule Below)
N 7 1s2 2s2 2px1 2py1 2pz1 or He 2s2 2px1 2py1 2pz1
O 8 1s2 2s2 2px2 2py1 2pz1 or He 2s2 2px2 2py1 2pz1
F 9 1s2 2s2 2px2 2py2 2pz1 or He 2s2 2px2 2py2 2pz1
Ne 10 1s2 2s2 2px2 2py2 2pz2 or He 2s2 2px2 2py2 2pz2
Na 11 1s2 2s2 2px2 2py2 2pz2 3s1 or Ne 3s1
Mg 12 1s2 2s2 2px2 2py2 2pz2 3s2 or Ne 3s2
Al 13 1s2 2s2 2px2 2py2 2pz2 3s2 3px1 or Ne 3s2 3px1
Si 14 1s2 2s2 2px2 2py2 2pz2 3s2 3px13py1 or Ne 3s2 3px1 3py1
P 15 1s2 2s2 2px2 2py2 2pz2 3s2 3px13py13pz1 or Ne 3s2 3px1 3py1 3pz1
S 16 1s2 2s2 2px2 2py2 2pz2 3s2 3px23py13pz1 or Ne 3s2 3px2 3py1 3pz1
Cl 17 1s2 2s2 2px2 2py2 2pz2 3s2 3px23py23pz1 or Ne 3s2 3px2 3py2 3pz1
Ar 18 1s2 2s2 2px2 2py2 2pz2 3s2 3px23py23pz2 or Ne 3s2 3px2 3py2 3pz2
K 19 1s2 2s2 2px2 2py2 2pz2 3s2 3px23py23pz2 4s1 or Ar 4s1
Ca 20 1s2 2s2 2px2 2py2 2pz2 3s2 3px23py23pz2 4s2 or Ar 4s2
Sc 21 Ar 4s2 3d1
Ti 22 Ar 4s2 3d1 3d1
V 23 Ar 4s2 3d1 3d1 3d1
Cr 24 Ar 4s1 3d1 3d1 3d1 3d13d1 (* see Hund’s Rule Below)
Mn 25 Ar 4s2 3d1 3d1 3d1 3d13d1
Fe 26 Ar 4s2 3d2 3d1 3d1 3d13d1
Co 27 Ar 4s2 3d2 3d2 3d1 3d13d1
Ni 28 Ar 4s2 3d2 3d2 3d2 3d13d1
Cu 29 Ar 4s1 3d2 3d2 3d2 3d23d2 (note that a 4s electron has moved to fill the 3d)
Zn 30 Ar 4s2 3d2 3d2 3d2 3d23d2 or Ar 4s2 3d10
Ga 31 Ar 4s2 3d2 3d2 3d2 3d23d2 4px1 or Ar 4s2 3d10 4px1
Ge 32 Ar 4s2 3d2 3d2 3d2 3d23d2 4px1 4py1 or Ar 4s2 3d10 4px1 4py1
As 33 Ar 4s2 3d2 3d2 3d2 3d23d2 4px1 4py1 3pz1 or Ar 4s2 3d10 4px1 4py1 3pz1
Se 34 Ar 4s2 3d2 3d2 3d2 3d23d2 4px2 4py1 4pz1 or Ar 4s2 3d10 4px2 4py1 4pz1
Br 35 Ar 4s2 3d2 3d2 3d2 3d23d2 4px2 4py2 4pz1 or Ar 4s2 3d10 4px2 4py2 4pz1
Kr 36 Ar 4s2 3d2 3d2 3d2 3d23d2 4px2 4py2 4pz2 or Ar 4s2 3d10 4p6
Rb 37 Kr 5s1
Sr 38 Kr 5s2
Hund’s Rule: Electrons line up in degenerate orbitals (orbitals of the same energy), one to each orbital, with parallel spins, before pairing. The effect of this rule may first be seen in C. After one electron enters the 2px , the next electron does not pair in the 2px but enters the 2py. Only after N, which has one electron in each of the three 2p orbitals, do electrons pair. An interesting effect may be seen when the 3d electrons fill. Not only do the electrons line up with parallel spins in each of the five 3d’s but in Cr, one of the 4s electrons is promoted to the 5th 3d orbital giving six orbitals with one electron in each!
Orbitals and the periodic table demonstrates how the periodicity in orbital structure appears on the periodic table.
——————————————————————————–
The Electron Configurations Worksheet
Quantum Numbers and Electron Configurations The Answers to this Worksheet
1. State the four quantum numbers and the possible values they may have.
2. Name the orbitals described by the following quantum numbers
a. n = 3, L = 0
b. n = 3, L = 1
c. n = 3, L = 2
d. n = 5, L = 0
3. Give the n and L values for the following orbitals
a. 1s
b. 3s
c. 2p
d. 4d
e. 5f
4. Place the following orbitals in order of increasing energy:
1s, 3s, 4s, 6s, 3d, 4f, 3p, 7s, 5d, 5p
5. What and the possible mL values for the following types of orbitals?
a. s
b. p
c. d
d. f
6. How many possible orbitals are there for n =
a. 4
b. 10
7. How many electrons can inhabit all of the n=4 orbitals?
8. Tabulate all of the possible orbitals (by name, i.e. 4s) for n=4 and give the three quantum numbers which define each orbital.
9. Write electron configurations for the following atoms:
a. H
b. Li
c. N
d. F
e. Br
——————————————————————————–
Answers
1. n may be any integer
L may be any integer from 0 to n-1
mL may be any integer from -L to +L
mS may be either + 1/2 or -1/2
2. a. 3s
b. 3p
c. 3d
d. 5s
3. a. n=1, L=0
b. n=3, L=0
c. n=2, L=1
d. n=4, L=2
e. n=5, L=3
4. 1s, 3s, 3p, 4s, 3d, 5p, 6s, 4f, 5d, 7s
5. a. 0
b. 1, 0, -1
c. 2, 1, 0, -1, -2
d. 3, 2, 1, 0, -1, -2, -3
6. a. 16
b. 100
7. 32
8.
name 4s 4p 4p 4p 4d 4d 4d 4d 4d 4f 4f 4f 4f 4f 4f 4f
n 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4
L 0 1 1 1 2 2 2 2 2 3 3 3 3 3 3 3
mL 0 1 0 -1 2 1 0 -1 -2 3 2 1 0 -1 -2 -3
9. a. 1s1
b. 1s2 2s1 or He 2s1
c. 1s2 2s2 2px1 2py1 2pz1 or He 2s2 2px1 2py1 2pz1 or He 2s2 2p3
d. 1s2 2s2 2px1 2py2 2pz2 or He 2s2 2px1 2py2 2pz2 or He 2s2 2p5
e. Ar 4s2 4px1 4py2 4pz2

There are equations in a field called quantum mechanics that describe the nature of electrons.
The inputs to the equations are the specific nature of what electrons we’re talking about. What atom is concerned, which electrons in that atom?
When the equations are solved, the solutions are characterized by certain numbers. These are the “quantum numbers” for that particular electron.
The equations are very very (keep putting verys on) difficult to solve. But the resulting quantum numbers for electrons follow relatively simple rules. So you can use the rules instead of solving the equations. Those rules are described in textbooks (your best source for explanation of the rules) and some explanations of those rules appear in other answers here.
The rules may look complex, and the reasons for them not perfectly clear. But the underlying thing is the solutions to those equations. The rules are a useful shortcut, the downside is that you can’t see the reasons why they are what they are.
That’s what quantum numbers are. Solutions to the quantum mechanics equations for electrons.

crap that sounds so familiar!!!!!!!!!!!!!!!!!

Each electron has a set of four numbers, called quantum numbers, that specify it completely; no two electrons in the same atom can have the same four

1. Principal (shell) quantum number – n

Describes the energy level within the atom.

o Energy levels are 1 to 7

o Maximum number of electrons in n is 2 n^2

2. Momentum (subshell) quantum number – l

Describes the sublevel in n

o Sublevels in the atoms of the known elements are s – p – d – f

o Each energy level has n sublevels.

o Sublevels of different energy levels may have overlapping energies.

The momentum quantum number also describes the shape of the orbital.

* Orbitals have shapes that are best described as spherical (l = 0), polar (l = 1), or cloverleaf (l = 2).

* Orbitals even take on more complex shapes as the value of the angular quantum number becomes larger.

3. Magnetic quantum number – m

Describes the orbital within a sublevel

o s has 1 orbital

o p has 3 orbitals

o d has 5 orbitals

o f has 7 orbitals

Orbitals contain 1 or 2 electrons, never more.

m also describes the direction, or orientation in space for the orbital.

4. Spin quantum number – s

This fourth quantum number describes the spin of the electron.

o Electrons in the same orbital must have opposite spins.

o Possible spins are clockwise or counterclockwise.

Rules governing the combinations of quantum numbers:

* Three quantum numbers n, l, and m are integers.

* The principal quantum number (n) cannot be zero.

o n must be 1, 2, 3, etc.

* The angular quantum number (l) can be any integer between 0 and n – 1.

o For n = 3, l can be either 0, 1, or 2.

* The magnetic quantum number (m) can be any integer between -l and +l.

o For l = 2, m can be either -2, -1, 0, +1, or +2.

* The spin quantum number (s) is arbitrarily assigned the numbers +1/2 and -1/2.

I’m thinking its 6, But maybe 2 points isn’t worth thinking bout this,,, ohhhhhh BRB Quantum Leap in on the psy-fi channel

An electrons quantum number is a series of 4 numbers.

The first is the [primary energy level, the second is the subshell, the third describes an orbital withing that subshell, and the last number is either +1/2 or-1/2 — this corresponds to the “spin” of the electron.

The first number can be 1-7, for the seven available energy levels of the known elements. (This corresponds directly to the seven rows of ther periodic table. As you move down rows you move up energy levels)

The second number is either 0, 1, 2, or 3. 0 is the s subshell, 1 is the p subshell, 2 is the d subshell, and 3 is the f subshell.

The third number describes orbitals within the subshell. It ranges from the negative to positive versions of the number of the shell in question. For example, if the second number is 2(d subshell), the third number can be -2, -1, 0, 1, 2. (This corresponds to the 5 orbitals found in the d subshell) If the second number is 1, the third number can be -1, 0 or 1 (Corresponding to the 3 orbitals of the p subshell) Remember each orbital holds two electorns.

The last number, no matter what, can be either +1/2 or -1/2 describing the two electrons within each orbital.

You can think of an quantum number as an address to find an electron — it directs you, more and more specifically, to an electrons “location”

Thats about as simple as I can make it.

There are four Quantum numbers.

they describe four factors that describe the energy of the electron. These four factors give a unique energy to any unique electron found in an atom.

The four Quantum numbers are as follows:.

Principle energy level

sub shell energy level

shell shape or orientation

spin of the electron in its orbital

the values of these four numbers can be put into an equation and a unique energy can be calculated for any electron in an atom.

A good article can be found at the web sight:

http://www.ux1.eiu.edu/~cfmdr/The%20Quantum%20Model%20Explained.pdf#search='quantum%20number%20explain‘

You’re kidding, right? A simple explanation of Quantum Numbers.

I hope you are taking either Quantum Theory or Physical Chemistry, so here goes.

There are 3 basic types of molecular motion: translation, rotation, and vibration. These are important because they are ways that molecules can store energy.

Translational motion occurs when molecules are in a container, and the kinetic energy of the total mass of molecules contributes to the total internal energy of the sample.

Molecules can rotate, and the transitions between allowed rotational energy levels are responsible for their spectra (individual wavelengths that can be measured).

Molecular bonds can vibrate, which is also a store of energy, and transitions give rise to vibrational spectra (also measurable).

Quantum numbers are the numbers assigned to describe each of the values for this energy.

Schrodinger’s Equation deals with these different forms of energy, and defines the three Quantum Numbers for :

Principal Quantum Number: n = 1,2,3,4,… infinity

Angular Momentum Quantum Number: l = 0,1,2,… n-1

Magnetic Quantum Number: m(subl) = l,l – 1, l – 2,…, – l

In addition, these are also considered Quantum Numbers:

Total Orbital Angular Momentum :

J = j1+ j2, j1 + j2 – 1,…, l j1 – j2 l

Total Angular Momentum:

L = l1 + l2, l1 + l2 – 1,….l l1 – l2 l (No absolute value bars, sorry)

Total Spin:

S = 1/2 + 1/2,1/2 + 1/2 – 1,…1/2 – 1/2

Electron Shell Number: s,p,d,f,…..

Electron Subshell Number: s=1,p=3,d=5,f=7

If you need further help, you may contact me and I will try to help you out. This is a complex subject, but I am considered a pretty good teacher, so i think I can help you.

The Quantum Numbers

name symbol values

Principal Quantum Number n any integer from 1 to infinity

Azimuthal Quantum Number L any integer from 0 to n-1

Magnetic Quantum Number mL any integer from -L to +L

Spin Quantum Number ms +/- 1/2

for the Worksheet

Generating a Table of Atomic Orbitals

Begin with the lowest value of n (n=1). Calculate all allowable values of L (in this case L =0, only). Name the orbital with the number of “n” and the letter which corresponds with “L,” according to the table below:

L-value orbital type

0 s

1 p

2 d

3 f

The orbital referred to above is the 1s orbital.

Orbitals are filled, lowest energy level first. The energy level of the orbital is approximated by adding the n and L values together and ordering the orbitals according to their n+L values. If n+L values are equal, orbitals with lower “n” values are filled first. According to the Pauli Exclusion Principle, no two electrons may have all four quantum numbers the same.

n L mL ms n+L orbital name order filled

1 0 0 +1/2, -1/2 1 1s 1

2 0 0 +1/2, -1/2 2 2s 2

2 1 -1 +1/2, -1/2 3 2px 3

2 1 0 +1/2, -1/2 3 2py 3

2 1 +1 +1/2, -1/2 3 2pz 3

3 0 0 +1/2, -1/2 3 3s 4

3 1 -1 +1/2, -1/2 4 3px 5

3 1 0 +1/2, -1/2 4 3py 5

3 1 +1 +1/2, -1/2 4 3pz 5

3 2 -2 +1/2, -1/2 5 3d 7

3 2 -1 +1/2, -1/2 5 3d 7

3 2 0 +1/2, -1/2 5 3d 7

3 2 +1 +1/2, -1/2 5 3d 7

3 2 +2 +1/2, -1/2 5 3d 7

4 0 0 +1/2, -1/2 4 4s 6

4 1 -1 +1/2, -1/2 5 4px 8

4 1 0 +1/2, -1/2 5 4py 8

4 1 +1 +1/2, -1/2 5 4pz 8

4 2 -2 +1/2, -1/2 6 4d 10

4 2 -1 +1/2, -1/2 6 4d 10

4 2 0 +1/2, -1/2 6 4d 10

4 2 +1 +1/2, -1/2 6 4d 10

4 2 +2 +1/2, -1/2 6 4d 10

4 3 -3 +1/2, -1/2 7 4f

4 3 -2 +1/2, -1/2 7 4f

4 3 -1 +1/2, -1/2 7 4f

4 3 0 +1/2, -1/2 7 4f

4 3 +1 +1/2, -1/2 7 4f

4 3 +2 +1/2, -1/2 7 4f

4 3 +3 +1/2, -1/2 7 4f

5 0 0 +1/2, -1/2 5 5s 9

5 1 -1 +1/2, -1/2 6 5px 11

5 1 0 +1/2, -1/2 6 5py 11

5 1 +1 +1/2, -1/2 6 5pz 11

etc

The sequence of orbitals just generated is

1s 2s 2px 2py 2pz 3s 3px 3py 3pz 4s 3d 3d 3d 3d 3d 4s 4px 4py 4pz 5s 4d 4d 4d 4d 4d 5px 5py 5pz 6s 5d 5d 5d 5d 5d 4f 4f 4f 4f 4f 4f 4f etc.

The fourth quantum number, the spin quantum number, allows two electrons of opposite spin (or symmetry) into each orbital. The electron configurations of several atoms are on the following table.

Some of the shortcuts employed in the table below are

using the symbol for the previous noble gas to represent all of the orbitals in that noble gas.

when the p or d orbitals are completely filled, expressing those as p6 or d10.

atom atomic number electron configuration

H 1 1s1 (meaning one electron in the 1s orbital)

He 2 1s2

Li 3 1s2 2s1 or He 2s1

Be 4 1s2 2s2 or He 2s2

B 5 1s2 2s2 2px1 or He 2s2 2px1

C 6 1s2 2s2 2px1 2py1 or He 2s2 2px1 2py1 (* see Hund’s Rule Below)

N 7 1s2 2s2 2px1 2py1 2pz1 or He 2s2 2px1 2py1 2pz1

O 8 1s2 2s2 2px2 2py1 2pz1 or He 2s2 2px2 2py1 2pz1

F 9 1s2 2s2 2px2 2py2 2pz1 or He 2s2 2px2 2py2 2pz1

Ne 10 1s2 2s2 2px2 2py2 2pz2 or He 2s2 2px2 2py2 2pz2

Na 11 1s2 2s2 2px2 2py2 2pz2 3s1 or Ne 3s1

Mg 12 1s2 2s2 2px2 2py2 2pz2 3s2 or Ne 3s2

Al 13 1s2 2s2 2px2 2py2 2pz2 3s2 3px1 or Ne 3s2 3px1

Si 14 1s2 2s2 2px2 2py2 2pz2 3s2 3px13py1 or Ne 3s2 3px1 3py1

P 15 1s2 2s2 2px2 2py2 2pz2 3s2 3px13py13pz1 or Ne 3s2 3px1 3py1 3pz1

S 16 1s2 2s2 2px2 2py2 2pz2 3s2 3px23py13pz1 or Ne 3s2 3px2 3py1 3pz1

Cl 17 1s2 2s2 2px2 2py2 2pz2 3s2 3px23py23pz1 or Ne 3s2 3px2 3py2 3pz1

Ar 18 1s2 2s2 2px2 2py2 2pz2 3s2 3px23py23pz2 or Ne 3s2 3px2 3py2 3pz2

K 19 1s2 2s2 2px2 2py2 2pz2 3s2 3px23py23pz2 4s1 or Ar 4s1

Ca 20 1s2 2s2 2px2 2py2 2pz2 3s2 3px23py23pz2 4s2 or Ar 4s2

Sc 21 Ar 4s2 3d1

Ti 22 Ar 4s2 3d1 3d1

V 23 Ar 4s2 3d1 3d1 3d1

Cr 24 Ar 4s1 3d1 3d1 3d1 3d13d1 (* see Hund’s Rule Below)

Mn 25 Ar 4s2 3d1 3d1 3d1 3d13d1

Fe 26 Ar 4s2 3d2 3d1 3d1 3d13d1

Co 27 Ar 4s2 3d2 3d2 3d1 3d13d1

Ni 28 Ar 4s2 3d2 3d2 3d2 3d13d1

Cu 29 Ar 4s1 3d2 3d2 3d2 3d23d2 (note that a 4s electron has moved to fill the 3d)

Zn 30 Ar 4s2 3d2 3d2 3d2 3d23d2 or Ar 4s2 3d10

Ga 31 Ar 4s2 3d2 3d2 3d2 3d23d2 4px1 or Ar 4s2 3d10 4px1

Ge 32 Ar 4s2 3d2 3d2 3d2 3d23d2 4px1 4py1 or Ar 4s2 3d10 4px1 4py1

As 33 Ar 4s2 3d2 3d2 3d2 3d23d2 4px1 4py1 3pz1 or Ar 4s2 3d10 4px1 4py1 3pz1

Se 34 Ar 4s2 3d2 3d2 3d2 3d23d2 4px2 4py1 4pz1 or Ar 4s2 3d10 4px2 4py1 4pz1

Br 35 Ar 4s2 3d2 3d2 3d2 3d23d2 4px2 4py2 4pz1 or Ar 4s2 3d10 4px2 4py2 4pz1

Kr 36 Ar 4s2 3d2 3d2 3d2 3d23d2 4px2 4py2 4pz2 or Ar 4s2 3d10 4p6

Rb 37 Kr 5s1

Sr 38 Kr 5s2

Hund’s Rule: Electrons line up in degenerate orbitals (orbitals of the same energy), one to each orbital, with parallel spins, before pairing. The effect of this rule may first be seen in C. After one electron enters the 2px , the next electron does not pair in the 2px but enters the 2py. Only after N, which has one electron in each of the three 2p orbitals, do electrons pair. An interesting effect may be seen when the 3d electrons fill. Not only do the electrons line up with parallel spins in each of the five 3d’s but in Cr, one of the 4s electrons is promoted to the 5th 3d orbital giving six orbitals with one electron in each!

Orbitals and the periodic table demonstrates how the periodicity in orbital structure appears on the periodic table.

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The Electron Configurations Worksheet

Quantum Numbers and Electron Configurations The Answers to this Worksheet

1. State the four quantum numbers and the possible values they may have.

2. Name the orbitals described by the following quantum numbers

a. n = 3, L = 0

b. n = 3, L = 1

c. n = 3, L = 2

d. n = 5, L = 0

3. Give the n and L values for the following orbitals

a. 1s

b. 3s

c. 2p

d. 4d

e. 5f

4. Place the following orbitals in order of increasing energy:

1s, 3s, 4s, 6s, 3d, 4f, 3p, 7s, 5d, 5p

5. What and the possible mL values for the following types of orbitals?

a. s

b. p

c. d

d. f

6. How many possible orbitals are there for n =

a. 4

b. 10

7. How many electrons can inhabit all of the n=4 orbitals?

8. Tabulate all of the possible orbitals (by name, i.e. 4s) for n=4 and give the three quantum numbers which define each orbital.

9. Write electron configurations for the following atoms:

a. H

b. Li

c. N

d. F

e. Br

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Answers

1. n may be any integer

L may be any integer from 0 to n-1

mL may be any integer from -L to +L

mS may be either + 1/2 or -1/2

2. a. 3s

b. 3p

c. 3d

d. 5s

3. a. n=1, L=0

b. n=3, L=0

c. n=2, L=1

d. n=4, L=2

e. n=5, L=3

4. 1s, 3s, 3p, 4s, 3d, 5p, 6s, 4f, 5d, 7s

5. a. 0

b. 1, 0, -1

c. 2, 1, 0, -1, -2

d. 3, 2, 1, 0, -1, -2, -3

6. a. 16

b. 100

7. 32

8.

name 4s 4p 4p 4p 4d 4d 4d 4d 4d 4f 4f 4f 4f 4f 4f 4f

n 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

L 0 1 1 1 2 2 2 2 2 3 3 3 3 3 3 3

mL 0 1 0 -1 2 1 0 -1 -2 3 2 1 0 -1 -2 -3

9. a. 1s1

b. 1s2 2s1 or He 2s1

c. 1s2 2s2 2px1 2py1 2pz1 or He 2s2 2px1 2py1 2pz1 or He 2s2 2p3

d. 1s2 2s2 2px1 2py2 2pz2 or He 2s2 2px1 2py2 2pz2 or He 2s2 2p5

e. Ar 4s2 4px1 4py2 4pz2

There are equations in a field called quantum mechanics that describe the nature of electrons.

The inputs to the equations are the specific nature of what electrons we’re talking about. What atom is concerned, which electrons in that atom?

When the equations are solved, the solutions are characterized by certain numbers. These are the “quantum numbers” for that particular electron.

The equations are very very (keep putting verys on) difficult to solve. But the resulting quantum numbers for electrons follow relatively simple rules. So you can use the rules instead of solving the equations. Those rules are described in textbooks (your best source for explanation of the rules) and some explanations of those rules appear in other answers here.

The rules may look complex, and the reasons for them not perfectly clear. But the underlying thing is the solutions to those equations. The rules are a useful shortcut, the downside is that you can’t see the reasons why they are what they are.

That’s what quantum numbers are. Solutions to the quantum mechanics equations for electrons.