October 7th

Cations and Dogions proudly presents:

The Quickie Chemistry Guide to Writing and Naming Ionic and Covalent Compounds
(now with helpful images and great resources!)

Ionic Compounds

C&D, what are ionic compounds?

Well, young one, just like how your mom and dad were attracted to each other when they first met, so too are the atoms of metals and the atoms of non-metals when they meet up.

Those smug noble gases...they
don't need to bond with anyone!

Unlike noble gases, which already have full valence (outer) electron shells, and are therefore stable, metals and other non-metals have incomplete valence shells. To make up for this, whenever a metal atom meets a non-metal atom, it will lose electrons and give them to the non-metal. This way, both atoms end up stable, with full valence shells.

When an atom gains or loses electrons, it becomes an electrically charged particle called an ion. In exchanging electrons, an ionic bond is formed between the atoms involved. These bonds are known as ionic compounds.

FREDDY!

Okay, so how do we "name" them? Can I call this one 'Freddy'?

Uh, no.

To name ionic compounds, first you must have a metal atom, and a non-metal atom (obviously). Let's take a pair at random from the Periodic Table of the Elements...Calcium (Ca) can be our metal, and...Chlorine (Cl) can be our non-metal!

Okay, so now you have your two elements. Looking at the common combining capacity for Calcium, you'll notice that it has a charge of +2. Now, look at the combining capacity for Chlorine. It's -1.

Two Rules that Must Be Followed:

1. In ionic compound naming, you always use the abbreviated name form of the element.
2. The name of the metal goes first.

In accordance with rule #2, Calcium will be first in the name.

Ca

Since Calcium has a charge of +2, Chlorine has to "keep even" with him (or her, as the case might be...). Since it's original charge is -1, we'll add TWO Chlorine ions to the Calcium ion, represented by a subscript 2 next to the "Cl" for "Chlorine". So in this bond, for every one Calcium, there are two Chlorines.

CaCl₂

Ta-daaaa!

But how do we know which combining capacity to use if there are TWO listed? Titanium (Ti), for example, has both a +4, and a +3!

They'll tell you, smarty. If it's Titanium with a +3 combining with oxygen, it will say titanium (III) oxide.

Which leads us to the reversal...

If given an ionic compound, and you want to write the original formula, just look up the name of the metal first. Then, look up the name of the non-metal, and drop the last few letters of the name and add on the ending "-ide" instead.

For example:

1. To revert FeN to the original name...first look up "Fe" to see that it stands for "Iron". ----> Iron
2. Next, look up "N" to see that it stands for "Nitrogen".
3. Since iron has two different charges (+2, +3), do a little bit of math. See that nitrogen has a +3 charge, and since FeN shows that no subscripts for N were needed, it's obvious that the "Fe" used was "Iron (III)", not "Iron (II)". ----> Iron (III)
4. Drop the "-rogen" off "nitrogen" and add on "-ide", to make ----> iron (III) nitride.

Some endings for non-metals:

bromine ---> bromide
oxygen ---> oxide
nitrogen ---> nitride
fluorine ---> fluoride
iodine ---> iodide
sulphur ---> sulphide
chlorine ---> chloride





^ Still not getting it? This nice lady can explain it to you in even further detail.



Covalent Compounds

C&D, what are covalent compounds?

Sharing is caring!

Well, young one, covalent compounds are chemical compounds that are formed when atoms share electrons rather than transfer them from one to another. Another key difference is that covalent compounds are formed between two non-metals, rather than a metal and a non-metal.

In covalent compounds, the ions are overlapping, as neither completely loses or gains the electrons involved in the process.

BOBBY!

Okay, so how do we "name" them? Can I call this one 'Bobby'?

Yes, of course! :)

...not.

To name covalent compounds, it's important to familiarize yourself with the Greek prefixes for the numbers. Why this is important will soon become very clear.

 

Number of Atoms	Prefix
1	mono- (use only for oxygen)
2	di-
3	tri-
4	tetra-
5	penta-
6	hexa-
7	hepta-
8	octa-
9	nona-
10	deca-

Now, say you want to get the original name for a covalent compound like N₂O₄.

You know that "N" is "nitrogen" and "O" is "oxygen".

No I don't...

Now you do. Now, you look back, and notice that there are two of nitrogen and four of oxygen. A quick glance at the table of Greek prefixes shows that "two" is "di-", and "four" is "tetra". Simply add those prefixes onto the respective element names.

Important Rule:

1. Remember in ionic compounds? How the second element changes its ending to "-ide"? Same rule applies here too.

Doing so, you get dinitrogen tetroxide. (Chemists have decided to chop off the "a" to make it sound prettier.)

Ohhhh, I get it! And when you're doing the reverse naming...?

Well, take a covalent compound like diphosphorus pentoxide. The Greek table tells you that "di" is "two", and "penta" is "five". So the formula would be P₂O₅.

That's all?

Well, yeah. It's pretty easy stuff.

Okies! (*^_^*)

^ The nice lady understands that an eleventh-grader can't possibly explain it any clearer than she can, obviously.


Extras:

Need more practice?

A quick review:

Mr. Monk's Ionic Compounds Quiz

Covalent Bonding

For those wanting a bit of a challenge:

Ionic Compounds

Covalent Compounds


Homework:

• Double-sided sheet of ionic and covalent naming questions that makes me want to kill myself