Valence Electrons and
Electron Configuration
Explaining the arrangement of
electrons
08/26 to 08/28
White Board Practice
• Use your lab materials to answer:
1. Ionization energy _______
from
Increases
left to right across a period.
2. Put the elements in order of
increasing ionization energy:
N, F, B, Li
Li, B, N, F
White Board Practice
• Use your lab materials to answer:
decreases from top
1. Ionization energy _______
to bottom down a group.
2. Put the elements in order of
increasing ionization energy:
Sr, Ca, Ba, Ra, Be
Ra, Ba, Sr, Ca, Be
White Board Practice
• Use your lab materials to answer:
Increases from left
1. Electronegativity_______
to right across a period.
2. Put the elements in order of
increasing Electronegativity:
Cl, P, S, Mg, Na
Na, Mg, P, S, Cl
Challenge: Cl, P, S, Ba, Cs
Cs, Ba, P, S, Cl
White Board Practice
• Use your lab materials to answer:
1. Electronegativity_______
decreases from top
to bottom down a group.
2. Put the elements in order of
increasing electronegativity:
Na, Rb, K, Li, Fr
Fr, Rb, K, Na, Li
Challenge: Na, K, Li, O, C
K, Na, Li, C, O
White Board Practice
• Use your lab materials to answer:
decreases
1. Atomic Radius_______
from left to
right across a period.
2. Put the elements in order of
increasing atomic radius:
Ca, Ti, Br, K
Br, Ti, Ca, K
Challenge: Li, Be, Na, K, O
O, Be, Li, Na, K
White Board Practice
• Use your lab materials to answer:
Increases
1. Atomic Radius_______
from top to
bottom down a group.
2. Put the elements in order of
increasing atomic radius:
Na, Rb, K, Li, Fr
Li, Na, K, Rb, Fr
Challenge: Na, K, Ra, B, F
F, B, Na, K, Ra
Unit 2 Intro
• Unit 2 is Chemical Bonds…
• Before we begin putting compounds
together we have to learn a few
more rules about atoms that will
help us predict what chemical bonds
will form.
Think Pair Share
• Describe the pictured substances.
White Board Practice:
Review
1. Why are the noble gases the least
reactive elements?
2. What are groups?
3. What are periods?
White Board Practice:
Answers
1. Why are the noble gases the least
reactive elements? They have a full
shell of valence electrons.
2. Groups are columns
3. Periods are rows
13 14 15 16 17 18
12
Write: groups tell us # valence electrons
1
2
3
4
5
6
7
Write: periods tell us energy levels
Unit 2 Day 1 Notes:
Electrons
• Take out a sheet of paper.
• Title it: Unit 2 Day 1 Notes: Electrons
Think, Pair, Share
• Answer the question at the top of your
notes:
• What does the number of protons tell
us about an atom?
• Answer: The number of protons
determines the atom’s identity.
Example: All carbon atoms have 6
protons.
Notes: Electrons
• Electrons determine the chemical
properties of an element.
• Only electrons react.
Notes: Electrons
• Valence electrons are electrons in the
outside energy level of an atom.
• Valence electrons participate in
chemical reactions.
This atom has 1
valence electron.
This is sodium.
1 question quiz!
Write the answer on your white
board:
• What on the periodic table tells us
how many valence electrons an atom
has?
Group 1 has 1 ve, group 2 has 2 ve, group 13 has
3, group 14 has 4, etc.
13 14 15 16 17 18
12
Write: groups tell us # valence electrons
Notes: Electrons
This atom has 1
valence electron.
This is sodium.
Na
• Lewis dot diagrams are a way to show
the number of valence electrons.
Notes: Ions!
• Octet Rule: To form ions, atoms give
or take enough electrons to have a
full outer energy level.
– They want the # of e- as the closest
noble gas. This is usually 8. (Exception:
Helium with 2.)
Ions Example
O
6 ve
Gain 2e-
O2-
Practice: Draw Lewis Dot Structures
and ions for elements 1-36
1. Fold you paper into an 8x4 grid. See the example.
2. Turn your paper so the long side is up.
3. Number the squares in the top left corner as
shown here:
1
In each square draw: (a) Lewis dot
diagram, (b) # valence electrons, (c) ion
formed
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
31
32
33
34
35
36
Practice: Draw Lewis Dot Structures
and ions
In each square draw:
(a) Lewis dot diagram,
(b) number valence
electrons,
(c) ion formed using
octet rule
3
Li
1 v.e.
Lose 1 eLi+
Practice: Draw Lewis Dot Structures
and ions
In each square draw: (a) Lewis dot diagram, (b)
# valence electrons, (c) ion formed
• Use octet rule for
ions. If you took
away e- the ion is +,
if you added e-, the
ion is -.
Li+
• Lewis Dot symbols
show us how many
valence electrons
are in an atom.
Li
Think, Pair, Share
• A positive ion is called a cation.
• A negative ion is called an anion.
Talk to your partner about which
atoms form cations and which form
anions.
Bonus Material
• Electron Configuration material is
advanced material.
Electron Configuration
• A way to keep track of all those
electrons!
• Write this down:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
http://www.youtube.com/watch?v=Vb6kAxwSWgU
Within the Energy Levels,
electrons are arranged in 1 or more
orbitals. Label the orbitals on
your periodic table.
S orbital
1
2
3
4
5
6
7
P orbital
D orbital
6
7
F orbital
© 1998 by Harcourt Brace & Company
Orbitals
Each orbital within a level has:
• different energies
• different shapes
• Different orientation in space
S
p
d
f
Periodic Table
&
Electron Configuration
• Example - Hydrogen
1
2
3
4
5
6
7
1
1s
1st Period
# e- in
sublevel
s-block
Periodic Table &
Electron Configuration
• Example - Carbon
1
2
3
4
5
6
7
X
XX
X
XX
2
2
2
1s 2s 2p
2nd Period
2 e- in p
sublevel
p-block
Short Hand Configuration
• Example - Carbon
1
2
3
4
5
6
7
X
X
XX
XX
2
2
[He]2s 2p
2nd Period
p-block
Notation
• Longhand Configuration
S 16e- 1s2 2s2 2p6 3s2 3p4
Core Electrons
(Inner orbitals)
Valence Electrons
(Outer shell)
• 1s2 2s2 Let’s
2p6 3s2Try
3p6 It!
4s2 3d10 4p6
Practice! Write the electron
configuration for the following
elements:
N, O, F, Ne, Na, Mg
Write your answers under your Bohr
models and Lewis Dot Structures for
these elements.