write any 100 ionic compounds with formulas..
Ionic compounds are basically defined as being compounds where two or more ions are held next to each other by electrical attraction. One of the ions has a positive charge (called a "cation") and the other has a negative charge ("anion"). Cations are usually metal atoms and anions are either nonmetals or polyatomic ions (ions with more than one atom). Think back to grade school: The same thing that makes the positive and negative ends of a magnet stick to each other is what makes cations and anions stick to each other.
Usually, when we have ionic compounds, they form large crystals that you can see with the naked eye. Table salt is one example of this - if you look at a crystal of salt, chances are you'll be able to see that it looks like a little cube. This is because salt likes to stack in little cube-shaped blocks.
Sometimes when you see a salt, it looks like a powder instead of a cube. This doesn't mean that the salt is not a crystal - it means that the crystals are just so small that you can't see them with the naked eye. If you were to put the powder under a microscope, chances are that you would see little geometric blocks.
So, what are the main properties of salts? Well, I'm sure glad you asked...
- All ionic compounds form crystals. So far as I know, there are no exceptions to this. Again, salts like to form crystals because when you have a whole bunch of little electrical positive and negative charges all stuck together, they seem to like to bunch into little stacking groups. The arrangement that these ions like to stack into is different, and is referred to as the "unit cell". There are ten or so different general shapes of unit cells. When you get to graduate school, ask me about them. For high school classes, it's really not all that important.
- Ionic compounds tend to have high melting and boiling points. When I say "high", what I mean is "very, very high." Most of the time, when you work with ionic compounds in a chemistry class, the melting point is hot enough that you can't melt them with a Bunsen burner. So, why are these temperatures so high? Well, it has to do with the way that ionic materials are held together. Remember how we said above that ionic compounds form crystals? These crystals are basically just great big blocks of positive and negative charges all stuck together. To break the positive and negative charges apart, it takes a huge amount of energy. This means that if we heat up the compound to add energy, it takes a huge amount of energy to break it apart.
- Ionic compounds are very hard and very brittle. Again, this is because of the way that they're held together. Above, we said that it takes a lot of energy to break the positive and negative charges apart from each other. This is the reason that ionic compounds are so hard - they simply don't want to move around much, so they don't bend at all. This also explains the brittleness of ionic compounds. It takes a lot of energy to pull ionic charges apart from each other. However, if we give a big crystal a strong enough whack with a hammer, we usually end up using so much energy to break the crystal that the crystal doesn't break in just one spot, but in a whole bunch of places. Instead of a clean break, it shatters.