Metals,, Intermonlecular Forces, and Water

This week we learned about metals, intermolecular forces, and water. We learned many things about metals through a POGIL . We learned that metals usually have the following properties:

• shine or luster
• are malleable, which means that they can be hammered into different shapes with out breaking. 
• are ductile, which means that they can be made into wire
• conduct electricity and heat

We were introduced to the concept of metallic bonding, and how it is different than ionic or covalent bonding. This is because the electrons from all of the metal ions are shared between more than 2 atoms. These electrons are delocalized from their original atom and this is called the sea of electrons.

In this picture you can see that there are lots of electrons around all of the ions. This is the sea of electrons.

Next we discussed the intermolecular forces which are also called van der Waals forces.  There are four types of van de Waals forces:

• dipole-dipole
• dipole-induced dipole
• induced dipole-induced dipole
• hydrogen bonding

Dipole-dipole  forces are intermolecular forces that from between polar molecules. Because there is a separation  of charges throughout the molecule, the negative part can attract a positive part of another molecule and visa verse. This is a relatively weak force and it only releases about 5 kJ/mol of energy when broken.

Dipole-induced dipole are forces that act between a polar molecule and a nonpolar molecule. When there different molecules come together the nonpolar molecule can have an induced dipole. This means that temporarily there will be a unequal distribution of charges in the nonpolar molecule. Dipole-induced dipole is the weakest intermolecular force. It only takes about 2 kJ/mol of energy to break theses bonds.

Induced dipol-induced dipole forces are forces that form between two nonpolar molecules. These are caused by the rapidly moving electrons about the molecules that cause a momentary change in the charge of molecules. These forces are also called London Dispersion Forces (LDFs). They have about the same energy as dipole-dipole forces, which is about 5 kL/mol energy to break them apart.

Hydrogen bonding is bonding between hydrogen atom that is covalently bonded to a oxygen, nitrogen, or fluorine atom that bonds with a different O, N, or F in a different molecule. An abundant example of hydrogen bonding would be in water. This compound is formed by many H2O molecules that are hydrogen bonded to each other. This is the strongest of the intermolecular forces, needing about 20 kJ/mol of energy to break.



The last thing that we discussed this week was about water and ice. We learned that when water freezes it expands. This is because it forms ridged hexagonal crystals that take up more volume than the liquid water. We constructed an ice cube using magnetic water molecules to simulate hydrogen bonding.

Notice how there are spaces in between the molecules in the ice and how all of the spaces are filled in the liquid water.


The last thing that we talked about regarding water was  ion-dipole interactions. We mainly focused on how this related to ions/ionic compounds dissolved in water.When an ionic compound is dissolved in water the cations become surrounded by the oxygen atoms in the water molecules and the anions become surrounded by the hydrogen atoms of the water molecules. If there is a stronger cation-anion force of attraction than the force of attraction from the water molecules the substance will not be soluble in water.

This week I think that I came to understand the intermolecular forces better. I now know that LDFs are a result of induced dipole-induced dipole interactions. I also think that this week has helped me fill in some of the gaps that I had regarding metals and ionic compounds dissolving in water. I would give my understanding of the week a 8/10 because I feel as if I understand the main concepts but I still want to study this material more to make sure that I am very comfortable with it.