12/15/08
Post date: Dec 15, 2008 2:18:58 AM
Bell Activity: Why do people form connections with other people?
Why chemical bonds form
Each atom wants to have a stable number of electrons
More atom anatomy
Charges
Atoms are made of protons, neutrons, and electrons
Protons have positive charge, electrons have a negative charge, neutrons have no charge
When not bonded, atoms have the same number of protons and neutrons, so net charge is 0
Electrons
Arranged in different levels or orbitals, with each level being able to hold a certain number of electrons
Valance electrons - the electrons in the outer-most level, involved in chemical bonding
Periodic table shows us how many valence electrons different atoms have by which column the element is in
Atoms want to have their outermost electron level filled up completely, and can do this in 2 ways
Take more electrons from another atom or give up electrons to another atom
When an atom gains electrons or gives them up, it is called an ion
Share electrons with another atom
These two methods result in 2 different types of bonds
Ionic bonds
Formed when one atom gives electrons to another
One atom is looking to get rid of electrons, another wants to get more, so electrons are transferred
The atom that gave up electrons has lost negative charge, and now has a positive charge. The atom that got more electrons has gained negative charge, and now has a negative charge. Since opposite charges attract, the positive ion is attracted to the negative ion.
Example: sodium bonding with chlorine
Sodium has 11 total electrons (atomic number is 11) and 1 of those is a valence electron (sodium is in the first column of the periodic table)
Chlorine has 17 total electrons (atomic number is 17) and 7 of those are valence electrons (7th column)
Sodium wants to get rid of one electron (so it has 8 valence electrons) and Chlorine wants to get one more electron (so it has 8 valence electrons)
Sodium gives one electron to Chlorine
Sodium (who lost one negative charge) now has a charge of +1 while Chlorine (who gained one negative charge) now has a charge of -1. The opposite charge attract each other, and the Sodium and Chlorine are pulled together.
Ionic analogy
In groups of 2 or 3, create an analogy for ionic bonds.
Write at least one paragraph explaining the analogy.
Present to the class tomorrow (Tuesday)
Example: My dog has 4 puppies, but I can only keep 2 of them. I give the other two to you, because you don't have any puppies and want 2. I then make it a point to keep in contact with you so that I can visit the other puppies, and we are thus "bonded" together.