Thursday
October 20, 2011
(Energy Levels,
Sublevels, and
Orbitals; Aufbau,
Hund, and Pauli)
Thursday, 10-20-11
Write the isotopic notation, electron
configuration notation, and Lewis Dot
Structure for the element uranium.
Summative
or
Formative
Date
Issued
Date
Due
Date
Into
Grade
Book
WS – The Periodic Law
(don’t do questions 9-11)
F
10/5
10/11
10/17
10/19
Test – Unit 3
S
10/11
10/11
10/12
10/26
WS - Valence Electrons
and Electron
Configuration
F
10/13
10/19
Lab – The Flame Test
F
10/14
10/17
Quiz – Valence Electrons,
Electron Configuration,
and Lewis Dot Structure
S
10/19
10/19
10/20
11/3
Assignment Currently
Open
Last
Day
Announcements
Worksheet - The Periodic Law – last day yesterday
Tomorrow you will have a substitute in this class.
You will take a Quiz, then begin work on the next
Worksheet.
Please work the entire period and treat your sub
with respect.
Thank you!
Main Energy Levels
An atom can have a maximum of 7 main
energy levels, which we have called “lanes
of the track.” These correspond to the 7
period of the Periodic Table.
Energy Sublevels
The main energy levels can further divided into sublevels,
which we call s, p, d, and f.
Energy level 1 – s-sublevel only
Energy level 2 – s- and p-sublevels
Energy level 3 – s-, p-, and d-sublevels
Energy level 4 – s-, p-, d-, and f-sublevels
Energy level 5 – s-, p-, d-, and f-sublevels
Energy level 6 – s-, p-, and d-sublevels
Energy level 7 – s-sublevel only (so far)
Remember that s-sublevels can hold up to 2 electrons, psublevels up to 6 electrons, d-sublevels up to 10 electrons,
and f-sublevels up to 14 electrons.
Electron Orbitals
An electron “orbital can hold only 2 electrons,
regardless of the energy sublevel it is in.
Since an s-sublevel can only hold 2 electrons, it can
contain only 1 orbital.
A p-sublevel can hold 6 electrons, so it can contain 3
orbitals.
A d-sublevel can hold 10 electrons, so it can contain 5
orbitals.
An f-sublevel can hold 14 electrons, so it can contain 7
orbitals.
Rules for Electrons in Orbitals
These three laws must be followed by
electrons in orbitals of an atomic cloud.
The Aufbau Principle
Hund’s Rule
The Pauli Exclusion Principle
The
Aufbau
Principle
An electron
occupies the
lowest energy
orbital that can
receive it
Example
The 4s orbital
is filled before
the 3d
Hund’s
Rule
Orbitals of equal
energy are each
occupied by one
electron before any
orbital is occupied
by a second
electron, and all
electrons in singly
occupied orbitals
must have the same
spin.
_____ _____ _____
2px
2py
2pz
Hund’s
Rule
Orbitals of equal
energy are each
occupied by one
electron before any
orbital is occupied
by a second
electron, and all
electrons in singly
occupied orbitals
must have the same
spin.
A school bus after a
rainstorm
All students will try
to get their own seat
on a separate row
until all rows are
filled with one
student. Only then
will they begin to
double-up.
The Pauli Exclusion Principle
No two electrons in the same
atom can have the same set of
four quantum numbers.
Electrons occur in pairs with
opposite spins.
The Principle Quantum Number
The principal quantum number (n) indicates
the main energy level occupied by the electron.
Values of n are positive integers only - 1, 2, 3,
and so on.
As n increases, the electron’s energy and its
average distance from the nucleus increase.
For example, an electron for which n = 1
occupies the first, or lowest, main energy level
and is located closest to the nucleus.
As you will see, more than one electron can have
the same n value, and these electrons are
sometimes said to be in the same electron shell.
The total number of orbitals that exist in a given
shell, or main energy level, is equal to n2.
The Angular Momentum Quantum Number
The angular momentum quantum number, (l),
indicates the shape of the orbital. Except at the
first main energy level, orbitals of different
shapes (known as sublevels) exist for a given
value of n. For a specific main energy level, the
number of orbital shapes possible is equal to n.
The values of l allowed are zero and all positive
integers less than or equal to n − 1. For
example, orbitals for which n = 2 can have one
of two shapes corresponding to l = 0 and l = 1
The Angular Momentum Quantum Number
Depending on its value of l, an
orbital is assigned a letter. s
orbitals are spherical, p orbitals
have dumbbell shapes, and d
orbitals are more complex. (The f
orbital shapes are too complex to
discuss here.) In the first energy
level, n = 1, there is only one
sublevel possible - an s orbital. As
mentioned, the second energy
level, n = 2, has two sublevels - the
s and p orbitals. The third energy
level, n = 3, has three sublevels the s, p, and d orbitals. The fourth
energy level, n = 4, has four
sublevels - the s, p, d, and f orbitals.
In an nth main energy level, there
are n sublevels
The Angular Momentum Quantum Number
Each atomic orbital is designated by the principal quantum number
followed by the letter of the sublevel. For example, the 1s sublevel is
the s orbital in the first main energy level, while the 2p sublevel is the
set of p orbitals in the second main energy level. On the other hand, a
4d orbital is part of the d sublevel in the fourth main energy level. How
would you designate the p sublevel in the third main energy level? How
many other sublevels are in the same main energy level with this one?
The Magnetic Quantum Number
The magnetic quantum number, (m),
indicates the orientation of an orbital
around the nucleus. Atomic orbitals can
have the same shape but different
orientations around the nucleus. Here
we describe the orbital orientations that
correspond to various values of m.
Because an s orbital is spherical and is
centered around the nucleus, it has only
one possible orientation. This
orientation corresponds to a magnetic
quantum number of m = 0. There is
therefore only one s orbital in each s
sublevel.
s-orbitals: m = 0
The Magnetic Quantum Number
The lobes of a p orbital can extend along the x, y, or z axis of a
three-dimensional coordinate system. There are therefore
three p orbitals in each p sublevel, which are designated as
px, py , and pz orbitals. The three p orbitals occupy different
regions of space and correspond, in no particular order, to
values of m = −1, m = 0, and m = +1 so far.
p-orbitals: m = -1, m = 0, m = +1
The Magnetic Quantum Number
There are five different d
orbitals in each d sublevel.
The five different orientations,
including one with a different
shape, correspond to values of
m = −2, m = −1, m = 0, m = +1,
and m = +2
The Magnetic Quantum Number
There are seven different f orbitals in each f sublevel. The total number
of orbitals at a main energy level increases with the value of n. In fact,
the number of orbitals at each main energy level equals the square of
the principal quantum number, n2. What is the total number of orbitals
in the third energy level? Specify each of the sublevels using the three
quantum numbers you’ve learned so far.
The Spin Quantum Number
Like Earth, an electron in an orbital can be thought of
as spinning on an internal axis. It spins in one of two
possible directions, or states. As it spins, it creates a
magnetic field. To account for the magnetic
properties of the electron, theoreticians of the early
twentieth century created the spin quantum number.
The spin quantum number has only two possible
values (+1/2 , −1/2) which indicate the two
fundamental spin states of an electron in an orbital. A
single orbital can hold a maximum of two electrons,
which must have opposite spins.
Example of Quantum Number Assignments
Carbon - 12
6 protons, 6 neutrons, 6 electrons
1s2, 2s2, 2p2
1s
2s
2px
2py
2pz
What is the quantum number set for this electron?
Angular
Primary
Magnetic
Spin
Momentum
2
1
0
+1/2