Transcript Wednesday, October 16, 2013

Wednesday, October 16, 2013
• You have ¼ sheet of paper with a food web
and 3 questions. Answer the questions and
clue the paper into your journal.
• We will be using the atom models again today.
Be sure to have your desk cleared of
everything except your journal and periodic
tables.
• Review quiz from yesterday.
Let’s Review
A=P=E
Atomic # = # Protons = # Electrons
1. How many electrons are in a neutral atom of Silicon?
2. If an atom has 8 protons (+) in the nucleus, what
element does it make up?
3. What charge is an atom that has the same number of
protons and electrons?
Let’s Review Some More
M–A=N
Atomic Mass # - Atomic # = # Neutrons
1.
2.
3.
4.
Neutrons are neutral (no charge) in the nucleus
The number of neutrons in an atom can change
Neutrons only add mass to the atom
The unit of measure for mass is amu (atomic mass
unit)
Energy Levels / Orbitals
• It is impossible to determine the exact location of
electrons in the atom at any one moment
• Electrons are more likely to be found in certain areas
within the vast electron cloud
• We designate energy levels / orbitals / rings / shells in
the electron cloud
• The first energy level can hold up to 2 electrons
• The second energy level can hold up to 8 electrons
• The third energy level can hold up to 8 electrons
• When diagramming atoms, the previous energy level
must be filled before moving to the next energy level
Can you identify this atom?
VALENCE ELECTRONS
• A valence electron is an electron in the outer
most shell
• Valence electrons determine an atom’s
reactivity
• Full orbitals 2 -8 -8 are  so they are not
reactive.
• If an orbital is not full, the atom is reactive.
• If atoms are reactive, they are involved in
chemical changes. (become compounds)
How many valence electrons does a
Lithium atom have?
Using Models
• Using the models, make a H atom.
• How many valence electrons?
• Is H reactive?
• Make a He atom.
• How many valence electrons in He?
• Is He reactive? Is He stable?