Electron Configuration

1
Electron Configuration

• Ch 13

2
Review

• 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)

3
Electron Configuration

• 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

4
Electron Configuration for Sodium

• 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

5

• 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?
• 22610 have been used
• 1 left over
• What sublevel does the one electron belong to?
• 3s

6
How to write Electron Configurations

• 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

7
Iron (Fe)

• 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.

8

• 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

9
Periodic Table and Electron Configurations

• 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
• Element is in groups 1 or 2
• p sublevel
• groups 13-18
• d sublevel
• groups 3-12
• f sublevel
• Element is a lanthanoid or actinoid

10
Kernel Structure

• 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)

11

• 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

12
Beryllium (Be)

• Kernel structure
• He2s1
• Long hand version
• 1s22s1

13

• What is the kernel structure for Selenium (Se)?
• First, what is the noble gas the period above
  selenium?
• Argon
• What period is Selenium in?
• 4th
• Kernel structure for selenium is
• Ar4s23d104p4

14

• 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