Valence Electrons and
Electron Configuration
Explaining the arrangement of
electrons
08/27 & 08/28
Catalyst
• Take out your HW to be stamped.
• On your Daily Work Organizer, fill in
your goal for the week.
• Catalyst: Describe the pictured
substances.
Video Clip: Review
http://www.youtube.com/watch?v=1PSzSTilu_s&feature=bf_prev&list=PL6
5159266CFC74682
Homework Baseball
Answer the questions on a blank sheet
of paper. Use your homework.
1. Why are the noble gases the least
reactive elements?
2. In the electron configuration 1s2,
the 1 represents the:
(a) number of protons
(b) number of electrons
(c) the energy level
Homework Baseball:
Answers
1. Why are the noble gases the least
reactive elements? They have a full
shell of valence electrons.
2. In the electron configuration 1s2,
the 1 represents the:
(a) number of protons
(b) number of electrons
(c) the energy level
Objectives
• SWBAT draw Lewis dot diagrams.
• SWBAT write electron configurations.
• SWBAT explain the octet rule and use it
to predict ion formation.
Agenda
•
•
•
•
Catalyst
Electrons and Intro to Ions
Mystery Elements Puzzle
Exit Ticket
Properties of the atom
• Protons determine the physical
properties
– The number of protons makes the element
• Electrons determine the chemical
properties
– Only the electrons react!!!
Electron Energy Levels
•In the electron cloud, electrons are arranged
in energy levels (aka orbitals or shells).
•Electrons fill the levels from the inside out.
•Electrons in the outer shell form chemical
bonds (react) with other atoms.
1
2
3
4
5
6
7
Write: periods tell us energy levels
What are valence
electrons??
• Valence electrons are electrons on
the outer shell of an atom that
are available for bonding.
– Valence Electrons are VERY
IMPORTANT, they determine an
element’s reactivity and general
characteristics
3 45678
12
Write: groups tell us # valence electrons
Practice: Draw the Bohr model and
Lewis Dot Structure for N, O, F, Ne,
Na, and Mg.
Note: 1st orbital has 2 e, 2nd and 3rd orbitals have
up to 8 e.
• Bohr models show
• Lewis Dot symbols
us all the electrons,
show us how many
separated by
valence electrons
energy level
are in an atom.
(orbital).
Li
Ions!
• Octet Rule: When forming ions,
atoms give or take electrons in
order to have a full outer orbital (or
shell).
– They end up with the same number of
electrons as the closest noble gas.
This is usually 8. (Exception: Helium
with 2.)
Think, pair, share.
• How many electrons would N, O, F,
Na, & Mg lose or gain to have the
same number of electrons as Ne?
• What ions are formed?
• Example: Lithium loses 1 e to form
Li+ (same # e as He)
(Work with the person next to you and
write your answers under your Lewis
Dot structures in your notes.)
Ions! Cations and Anions
• Ion = an atom that has gained or lost
electrons
– Ions have a negative or positive charge.
• Anion = ion with a negative charge.
– Usually nonmetals
• Ex: Cl- S2-
• Cation = ion with a positive charge.
– Usually metals
• Ex: Be2+ Al3+
Think, Pair, Share
• Are the ions of N, O, F, Na, and Mg
cations or anions?
– Label them in your notes.
– Then share with your partner.
• Does Ne form an ion? Why not?
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.
Agenda
•
•
•
•
Catalyst
Electrons and Intro to Ions
Mystery Elements Puzzle
Exit Ticket
Mystery Elements Puzzle
• Work in a group of 4 at your table
• Use the clues and your periodic
table to match each symbol with an
element.
• Write down your answers on a sheet
of paper.
• Raise your hand when you think you
have solved the puzzle.
Exit Ticket
1. Draw the Bohr model and Lewis
Dot Structure for Phosphorus (P).
2. Write the electron configuration of
P.
3. How many electrons will P lose or
gain to form an ion? How do you
know?
4. What ion does P form? Is it an
anion or cation?
If you are done, work on HW packet.