Quantum Numbers (1).pdf

quantum numbers

2. Quantum
Numbers

3. Four Quantum Numbers That
Describes Electrons
principal
quantum
number (n)
angular
momentum
quantum
number (ℓ)
magnetic
quantum
number (m
ℓ)
spin quantum
number (m
s)

4. principal quantum number (n)
The principal quantum number (n), describes the energy of the electron.
The energy of the electron is determined by its average distance from the nucleus
or the principal energy level where it is.
The larger n is, the greater the average distance of an electron in the orbital from
the nucleus and therefore the larger (and less stable) the orbital.
The maximum number of electrons possible in a given shell is 2n2 .

5. LEVEL MAXIMUM NUMBER OF ELECTRONS
n = 1
n = 2
n = 3
n = 4
n = 5
n = 6
n = 7

6. azimuthal or
angular
momentum
quantum
number (ℓ)
•Theazimuthalorangularmomentum
quantumnumber(ℓ),tellsusthe
“shape”oftheorbital.
•Itdesignatesthesublevelwhichthe
electronissaidtooccupy.
•Itisalsoaninteger,butitsvaluesare
limitedtoarangeof0ton-1.

7. ℓ 0 1 2 3 4 5
Name of
orbital
spdfgh

9. magnetic quantum
number (m
ℓ)
The magnetic quantum number
(mℓ) describes the orientation of
the orbital in space.
The number is also an integer, and
its values are restricted to a range
of +1 down through 0 to -1.

10. spin quantum number (m
s)
The spin quantum number (ms) refers to the “spin” of an electron in a
givenorbital.
It can have only two values: arrow up ↑ is +1/2( referred to as “spin up”)
and arrow down ↓ is -1/2 ( referred to as “spin down”).
The spin of an electron can be one of two opposite directions, clockwise
or counterclockwise.
Since the spin quantum number has only two possible values, it follows
that an orbital can accommodate a maximum of two electrons only

11. Electron
Configuration

12. Electron Configuration
Thearrangementofelectronsinanatomiscalledtheatom’s
electronicconfiguration.Theelectronconfigurationofanatomor
elementdescribeshowelectronsaredistributedinitsatomic
orbitals.Sincelow-energysystemsaremorestablethanhigh-energy
systems,electronsinanatomtendtoassumethearrangementthat
givestheatomthelowestenergypossible.Themoststable,lowest
energyarrangementoftheelectronsiscalledground-stateelectron
configurationofanelement.

13. Electron configurations are based
primarily on three principles:
Aufbau
principle
Pauli
exclusion
principle
Hund’s Rule

14. The Aufbau
Principle
•Aufbau principle is named after the German
word “Aufbeen” which means “build up”.
•The Aufbau principle dictates that electrons
will occupy the orbitals having lower
energies before occupying higher energy
orbitals based on the principal energy levels
and sublevels where they are in.

15. The Pauli
Exclusion
Principle
•Electronsinorbitalscanberepresentedby
arrowsinboxes.Anelectronisabletospinin
onlyoneofthetwodirections.Anarrow
pointinguprepresentsanelectronwhichis
spinninginonedirection,andanarrow
pointingdownmeansthattheelectronis
spinningintheoppositedirection.
•ThePauliexclusionprinciplestatesthat“a
maximumoftwoelectrons,eachhaving
oppositespins,canfitinasingleatomic
orbital.”WolfgangPauli(1900-1958),an
Austrianphysicist,proposedthisprinciple
afterobservingatomsinexcitedstates.

16. Hund’s Rule
of
Maximum
Multiplicity
•Thisruledescribestheorderinwhich
electronsarefilledinalltheorbitals
belongingtoasubshell.
•Itstatesthat“everyorbitalinagiven
subshellaresinglyoccupiedbyelectrons
beforeasecondelectronisfilledinan
orbital.”

17. Electron
Distribution

18. Electron
configuration
•Electron configuration uses the
symbols of the orbitals and the
number of electrons (written as
superscripts) that occupy each

19. Orbital
Diagram
•Orbitaldiagramconsistsofboxes
andarrowsthatrepresentthe
orbitalsandtheelectrons,
respectively.Eachboxislabeled
withtheprincipalquantum
numberandsublevelassociated
withtheorbital.

20. Noble Gas
Notation
•A shorthand method of writing electron
configuration of atoms uses the noble gases
core such as [He core] to represent 1s2; [Ne
core] to represent the 1s
2
2s
2
2p
6
; and other
noble gases.

22. Importantdatathatcanbegatheredfromthe
shortenedelectronicconfigurationarethe
valenceconfigurationandthevalence
electrons:thenumberofelectronsinthe
outermostsubshells.

23. Valence Configuration & Valence Electrons
•The electronic
configuration representing
the outermost subshells is
called valence
configuration.
•Electrons in the outermost
main energy level or
orbital are called valence
electrons.

24. Electron-dot
Structure

25. Valence Electrons & Electron-dot
Structure
Valence electrons are involved
in forming chemical bonds.
Chemists used a shorthand
method to visually represent
valence electrons. This is
called as the electron-dot
structure.
An atom’s electron-dot
consists of the element’s
symbol, which represents the
atomic nucleus and inner-level
electrons, surrounded by dots
representing all of the atom’s
valence electrons

26. Steps in
writing the
electron-dot
structure of an
atom:
1.Write the symbol of the given
atom.
2.Determine its valence electron.
This is equal to the number of
dots at the sides of the atom.
3.Draw a dot or dots to represent
the valence electron/s one at a
time on the four sides of the
symbol. (Dots may be placed in
a sequence.)
4.Then paired up the dots.

27. Ionic Lewis Dot Structures
1.Sodium,
11Na, combines with chlorine,
17Cl, to form sodium chloride
(table salt), NaCl.

28. Ionic Lewis Dot Structures
2.Potassium atom,
19K, combines with bromine atom,
9F, to form
potassium bromide, KF.