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 = EAtomic # = # 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 = NAtomic Mass # - Atomic # = # Neutrons

1. Neutrons are neutral (no charge) in the nucleus2. The number of neutrons in an atom can change3. Neutrons only add mass to the atom 4. 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?