Monday, October 18, 2010

Review from Science 10 when we were Oh So young and uncivilized: Writing + Naming Ionic and Covalent Compounds

So, today we are doing review on Science 10. Doesn't it feel like ages ago? One year later, of course, we're much more civilized and cultivated (oh big word).

The lesson today was on writing and naming Ionic and Covalent Compounds (as you can probably plainly see from the title). Does it sound fascinating? Well GOLLY GEE it sure was.

Well, lets start off with explaining what ions are. Ions are atoms or groups of atoms that are positively or negatively charged. Basically, they are composed of two or more oppositely charged particles (which are ions). They are held together by electrostatic forces (ooo :D)

In ionic compounds, electrons are transferred from a metal to a non metal. When writing Ionic Compounds, I LOVE doing the switch method. It's the easiest to understand. Hehe. What happens is the two particles switch charges.
For Example:
Strontium Fluoride
Strontium has a charge of +2
Fluoride has a charge of -1
So, that's Sr2F. BUT since they switch charges, it becomes SrF2

Simple enough? Well too bad, now it gets harder. If the charges are the same, they both canacel out.
For example:
Calcium Sulphide
Calcium has a charge of +2
Sulphur has a charge of -2
When this happens, DO NOT (under any circumstances, even if your dog is dying) write Ca2S2. WRONG WRONG WRONG WRONG WRONG.
The two's cancel out and that makes CaS.

Lastly, you need to know what happens when you have numbers that can easily divide into eachother
For Example:
Rhodium (IV) Oxide
Rhodium has a charge of +4
Oxygen has a charge of -2
So the equation is Rh2O4. BUT *gasp* there is a catch, this formula can reduce!!!
2 can easily divide into 4 because 4/2 = 2 (I hope you already know that but if you're suddenly brain dead, I wrote it out for you. It's okay, I have brain farts all the time).
SOOO...the formula becomes RhO2 because the simplifying cancelled out the 2 on rhodium and made the 4 a 2 on oxygen.
You see how that works? MAGICAL!

So now, we can finally move on to naming Ionic Compounds =.=

Okay so just to review a bit from last year, the metal is ALWAYS first and the non-metal is ALWAYS second. (Don't you feel bad that it always has to come in second? D:)

When naming, you need to change the ending of the non-metals to "ide"
For example:
Sulphur becomes Sulphide
Oxygen becomes Oxide
Fluorine becomes Fluoride
And it goes on and on and on and ooonn, strangers, waiting, up and down the boulevaarrdd. (okay i got carried away).

When the particle has more than 1 charge, you need to state the charge in roman numerals after the name of the particle.
For example:
FeO = Iron (II) Oxide
PbCl4 = Lead (IV) Chloride
If you do not remember your roman numerals (which I totally understand) I will be kind enough to write them out for you :)

1 = I 3 = III 5 = V
2 = II 4 = IV 6 = VI

Okay guys, we're now moving on to covalent compounds oooo, ahhh, ohhh. yes.
So covalent compounds, unlike ionic compounds, are between a non metal and non metal. They share electrons. Writing covalent compounds have the same rules as writing ionic compounds, but naming them is a different story.

Covalent compounds use Greek prefixes to indicate the number of atoms. Ohoho what is this? It appears we are taking a trip back YET AGAIN to ancient greece.

To truly understand the naming of covalent compounds, we must understand the Greek ways of numbering.

Mono = 1 Penta = 5 Nona = 9
Di = 2 Hexa = 6 Deca = 10
Tri = 3 Hepta = 7
Tetra = 4 Octa = 8

You need to put the greek prefixes infront of the particles names.
For example:
NH3 = Nitrogen trihydride
You do not need to put a "mono" infront of nitrogen even though it only has one atom, because you don't need to for the first particle.

The last thing you folks need to remember is the Diatomic Molecules. These are:

Hydrogen, Oxygen, Fluorine, Bromine, Iodine, Nitrogen, and Chlorine.

OR better known as
(prounounced Hoffbrinkle)
These all have two atoms:
H2, O2, F2, Br2, I2, N2, Cl2

When named, you must put a "gas" behind them.
For Example:
H2 = Hydrogen Gas
O2 = Oxygen Gas
F2 = Fluorine Gas

WELL THANKS FOR READING. I KNOW IT WAS A LOT. Now you may rest your eyes from staring at this screen. Researchers say it is bad to stare at a computer for more than two hours at a time. o.o



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