Ch 13
7

energy levels electrons can be found in
As the number of electrons increases, you fill
more energy levels
 Each
energy level contains certain sublevels
that hold a specific number of electrons

s (holds 2 electrons), p (6), d (10), f(14)
 Arrangement
of electrons in the energy
levels and sublevels


Always fill the lowest energy sublevel first
Use Aufbau principle to correctly fill the energy
levels and sublevels in order
 How

many electrons does Sodium (Na) have?
11
 What

is the first sublevel electrons fill?
1s
 How
many electrons can fit in the 1s
sublevel?

2
 What

is the second sublevel electrons fill?
2s
 How
many electrons can fit in the 2s
sublevel?

2
 What

is filled after the 2s sublevel?
2p
 How
many electrons can fit in the 2p
sublevel?

6
 How
many electrons are left that need a
sublevel?


2+2+6=10 have been used
1 left over
 What
to?

3s
sublevel does the one electron belong
 Write
the sublevels in order from least
energy to most energy
 Write the total number of electrons in each
sublevel as a superscript off the sublevel
 Example: Sodium (Na)

1s22s22p63s1
 How

many electrons does Fe have?
26
 What

is the electron configuration for Fe?
1s22s22p63s23p64s23d6
*Remember the 3d sublevel has more energy than
the 4s energy level so you fill the 4s sublevel
first.
•
What element has the electron configuration
1s22s22p63s23p64s23d104p3?

If you count the electrons, you can
then use that to determine the atomic
number and name of the element.

Since there are 33 electrons, the element is As

periodic table shows periodicity,
elements in the same group have similar properties
 Holds true for electron configurations


The last sublevel you fill relates to what group
you are in

If last sublevel to fill is the s sublevel


p sublevel


groups 13-18
d sublevel


Element is in groups 1 or 2
groups 3-12
f sublevel

Element is a lanthanoid or actinoid
 Short
hand way to show electron configuration
 To write a kernel structure

Need to know the noble gas that comes before the element
you are writing the kernel structure for

Example:
 What is the noble gas that comes before Beryllium (Be)?

Helium (He)
 Write
the symbol of the noble gas within
brackets

[He]
 Then
follow with the rest of the elements
electron configuration

Whenever you are writing kernel structures


Noble gas is always followed by a s sublevel
The period of the element that follows your noble gas
will tell you the energy level you are in
 Kernel

[He]2s1
 Long

structure
hand version:
1s22s1
 What

First, what is the noble gas the period above selenium?


Argon
What period is Selenium in?


is the kernel structure for Selenium (Se)?
4th
Kernel structure for selenium is:

[Ar]4s23d104p4
 What
are the only 2 elements that do not
have kernel structures?



H and He
Because there is no noble gas that precedes them
Therefore, always write long hand electron
configuration