# Isotope Formulas_ Quantum Numbers _amp; Electron Configurations

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```					Isotope Formulae,
Quantum Numbers
& Electron
Configurations

…pretty lofty stuff
Isotope Formulae
• Provide element’s symbol
• Mass number
– mass# = #p+ + #n
– written as a superscript to the left
• Atomic number
– atomic# = #p+ or #e-
– written as a subscript to the left
Isotope Formulae
Mass#
Atomic#
X
Carbon has two naturally occurring isotopes:
carbon-12 and carbon-13

12                       13
6
C                       6
C
Isotope Formulae
Give the isotope formula for each of the
following:
3
1. Hydrogen with 2 neutrons
1
H
18
2. Fluorine with 9 neutrons
9
F
235
3. Uranium with 143 neutrons
92
U
Valence Electron(s)
• The electron(s) farthest from
the nucleus or in the outermost
energy level.
Aufbau Principle
• Comes from German word
meaning “to build”
• Electrons will occupy lower
energy orbitals first
Pauli Exclusion
Principle
• An atomic orbital can hold at
most two electrons.
• If an atomic orbital holds two
electrons, they must have
opposite spins.
Hund’s Rule
• When filling atomic orbitals of
equal energy, place electrons
with parallel spins in the
orbitals first. Then, place the
oppositely spinning electrons
in to the orbitals.
Quantum Numbers
• Describe where electrons live
within an atom
• Four quantum numbers for
every electron of every atom
Quantum Numbers
• Principal (n)
– Describes the energy level in
which the electron lives
– May be any positive integer
– Thus, 1, 2, 3, etc.
Quantum Numbers
• Azimuthal or angular mometum (l )
– Azimuth means course or bearing
– Describes the shape of the pathway
that the electron takes or the shape of
the atomic orbital
– May be any integer from zero to (n-
1)…it’s dependent on “n”
– Thus, when n=1, l can only be 0
Quantum Numbers
• Magnetic (ml )
– Describes the orientation of the
atomic orbital in 3-D space
– May range from -l to +l …it’s
dependent on “l” which is dependent
on “n”
– Thus, when n=1, l can only be 0, and
ml can only be 0
– When n=2, l can be 0 or 1, and when
l is 1, ml can be –1, 0, or +1…or
three places in space
Quantum Numbers
• Spin (ms )
– Describes the spin of the electron
– May be either –½or +½, it’s
dependent upon none of the other
quantum numbers
– Thus, when n=1, l can only be 0, and
ml can only be 0, but ms can be
either –½or +½
The Quantum Numbers

name                symbol                  values

Principal Quantum                          any positive integer
n
Number                                 from 1 to infinity

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

Magnetic Quantum            ml            any integer from -l to +l
Number

Spin Quantum
ms                   - ½ or + ½
Number
Quantum Numbers
• What are the four quantum
numbers of hydrogen’s electron?

n=1
l=0
ml = 0
ms = –½
Quantum Numbers
• What are the four quantum
numbers of all of boron’s five
electrons?
n=1       n=1       n=2       n=2       n=2
l=0       l=0       l=0       l=0       l=1
ml = 0    ml = 0    ml = 0    ml = 0    ml = -1
ms = –½   ms = +½   ms = -½   ms = +½   ms = -½
Quantum Numbers
• What are the four quantum
numbers of sodium’s valence
electron?
n=3
l=0
ml = 0
ms = –½
Electron Configurations
• Also describe where electrons
live within an atom
• It’s like a translation of
quantum numbers.
• They give the energy level,
atomic orbital, and number of
electrons residing in the
orbital and energy level.
Electron Configurations
• Energy level
– May be any positive integer
– Just like the principal quantum
number
Electron Configurations
• Atomic Orbital or Sublevel
– Represented by letters: s, p, d, f
– Translates azimuthal number
and magnetic number
– s is the same as l = 0
– p is the same as l = 1
– d is the same as l = 2
– f is the same as l = 3
Electron Configurations
• Number of Electrons
– in either an atomic orbital or a
sublevel
– max of 2 in the s sublevel
– max of 6 in the p sublevel
– max of 10 in the d sublevel
– max of 14 in the f sublevel
Electron Configurations
• Use the periodic table to guide
you in writing electron
configurations.
• Find the link between 2,6,10,
and 14 and the periodic table.
Electron Configurations
• What are the four quantum numbers of
hydrogen’s electron? What is the
electron configuration of hydrogen?
# of
n=1           energy
1s 1       electrons
level
l=0
ml = 0                 sublevel/
orbital
ms = –½
Electron Configurations
• Write the e- configurations of the
next 9 elements (through Ne).
He…1s2

Li…   1s22s1     Look at the sum
of the superscripts…
Be… 1s22s2

B… 1s22s22p1
Electron Configurations
C…  1s22s22p2

N… 1s22s22p3
O… 1s22s22p4
F… 1s22s22p5

Ne…1s22s22p6
Electron Configurations
• Shorthand configurations are
written by assuming that you can
let the symbol of the noble gas
preceding the valence electrons
represent the e- configuration to
that point.
Electron Configurations
…shorthand
He…1s2
Li… [He]2s1
Be… [He]2s2
B… [He]2s 22p1

C… [He]2s 22p2
Electron Configurations
…shorthand
N… [He]2s22p3
O… [He] 2s22p4
F… [He] 2s22p5

Ne…[He] 2s22p6
Electron Configurations
…shorthand
Na… [Ne]3s1
Si… [Ne] 3s23p2
Cl… [Ne] 3s23p5

Ar… [Ne] 3s23p6
Electron Configurations
…shorthand
Ca…[Ar]4s2
Sc… [Ar] 4s23d1
Mn…[Ar] 4s 23d5

Se… [Ar] 4s23d104p4
Electron Configurations
…shorthand
I… [Kr] 5s24d105p5
La… [Xe] 6s25d1
Ce…[Xe] 6s 25d14f1

Hg…[Xe] 6s24f145d10
Exceptional Electron
Configurations…shorthand
Cr… [Ar] 4s23d4 [Ar] 4s13d5
Cu…[Ar] 4s23d9 [Ar] 4s13d10
Mo…[Kr] 5s 24d4 [Kr] 5s14d5

Ag…[Kr] 5s24d9 [Kr] 5s14d10
Orbital Diagrams
• Show the electron configuration
while illustrating the Aufbau
Principle, Pauli Exclusion
Principle, and Hund’s Rule
• Place energy on the y-axis
• Use lines to represent orbitals
• Use up and down arrows to
indicate spin
Orbital Diagrams (template)
3px   3py   3pz

3s

E   2px   2py   2pz

2s

1s
Orbital Diagram for H
3px   3py   3pz

3s

E    2px   2py   2pz

2s

1s
Orbital Diagram for He
3px   3py   3pz

3s

E    2px   2py   2pz

2s

1s
Orbital Diagram for Be
3px   3py   3pz

3s

E    2px   2py   2pz

2s

1s
Orbital Diagram for C
3px   3py   3pz

3s

E    2px   2py   2pz

2s

1s
Orbital Diagram for O
3px   3py   3pz

3s

E    2px   2py   2pz

2s

1s
Orbital Diagram for P
3px   3py   3pz

3s

E   2px   2py   2pz

2s

1s
Wrap-Up
• Write the 4 quantum numbers for
each of nitrogen’s 7 electrons.
• Write the electron configuration
for nitrogen.
• Write the orbital diagram for
nitrogen.

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