Unit 4:The Electron

1
Unit 4The Electron

• Part 3 Electron Configurations Using the
  Diagonal Rule Lewis Dot

2
Electron Configurations

• Show the arrangement of electrons in an atom the
  address
• Describes where the electrons are found and what
  energies they possess.
• Usually represent the ground state of the
  electrons.

3
Electron Configuration

• EXAMPLE 1s22s22p63s1 Sodium (Na) which is
  Atomic 11
• Shows the distribution of electrons among the
  orbitals of an atom.
• Describes where the electrons are located and how
  much energy each one has.
• Outer electrons (valence electrons) are critical
  for bonding

4
Determining Electron Configurations

• EXAMPLE 1s22s22p63s1
• Superscript of e-
• 2261 11 (Sodium)

5
Diagonal Rule

• 1s2
• 2s2 2p6
• 3s2 3p6 3d10
• 4s2 4s6 4d10 4f14
• 5s2 5s6 5d10 5f14
• 6s2 6p6 6d10 6f14
• 7s2 7p6 7d10 7f14

6
Using the Diagonal Rule

• Example 1 Helium atomic 2 2p 2e-
• Ans 1s2
• Example 2 Lithium atomic 3 3p 3e-
• Ans 1s22s1
• Example 3 Beryllium atomic 4 4p 4e-
• Ans 1s22s2
• Example 4 Silicon atomic 14 14p14e-
• Ans 1s22s22p63s23p2

7
Analyzing Electron Configs

• An atom of nitrogen has 7 electrons arranged in
  the following order 1s22s22p3
• or 1s22s22p3
• Nitrogens electrons require two energy levels.
  (Highest quantum number is n2.)
• It has 5 electrons in its highest level 23.
• Superscripts must add up to the atomic number of
  the element. (p e-)
• Nitorgen has 7 electrons total (223)

8
Rules for Electron Configuration

• Aufbau Principle - Electrons enter orbitals of
  lowest energy level first.
• Pauli Exclusion Principle An sub level can hold
  a maximum of 2 electrons. To occupy the same
  sublevel, the 2 electrons must spin in opposite
  directions.
• Hunds Rule - one electron enters each sub level
  until each sub level contains one electron with
  parallel spins before a second electron is added.

9
Lewis Dot Structures

• Another type of atomic model
• Consists of the elements symbol and the atoms
  valence electrons.
• Symbol kernel (represents the protons, neutrons
  and full electron shells).
• Dots valence electrons.
• EX

B
10
You can use the Electron Config to get the Lewis
Dot Structure

• Ca
• 1s22s22p63s23p64s2
• Locate the highest quantum number. (4)
• Add the s and p orbital electrons, and place them
  around the element symbol. (2)
• Look how easy this is with the short form.
• Ar4s2

Ca
11
One Final Example

• Tin
• 1s22s22p63s23p64s23d104p65s24d105p2
• Or
• Kr5s24d105p2
• Locate the highest quantum number (5)
• Add the s and p orbital electrons (4)

Sn
12
First two dots represent the s orbital electrons
and are placed at the top of the elements
symbol. Then the p orbital electrons are placed
in this order right, bottom, left, right,
bottom, left.
1
2
3
8
Ne
5
6
4
7