Covalence: (n) the number of electron pairs that an atom can share with other atoms.

Remember high school chemistry? The property of covalence is what allows atoms to form bonds with other atoms thereby creating molecules.

Today, Meredith Corporation, a magazine publisher, announced that it was acquiring a second ad agency. Specifically, an interactive shop. The reason behind this: to bolster the marketing services that the publisher provides to its advertisers.

Wait. Don’t ad agencies do that?

Right. These days, it’s getting fuzzier and fuzzier who does what. For example, Interpublic, an ad agency, just bought a major stake in Facebook.com, a social networking site.

Why is all this happening? Because the old ad-supported content model is breaking or broken. People are going to new places to consume content, ads are being zapped by TiVo, media is fragmented and therefore consumers are harder to reach.

These facts are old news. The NEW piece is this: In 2007 and forward, advertising must be MUCH MUCH smarter and woven with content in a completely new and innovative way that no one has really defined as yet. Advertising can’t compromise content. And also it has to work for advertisers. Really work. Not just pretend work. The days of being able to say, “Half your ad dollars are wasted, you just don’t know which half,” are over.

The old model was easy: Piece of content, interrupt with ad, now back to our show. If the ad doesn’t work, refer to the half-you-dollars-wasted principle. One more cushy reality eliminated by technology.

Now, advertisers and content producers must strive for Covalence.

The property that allows one chemical element to combine with another in this sense allows a piece of content to combine with certain types of advertising. The weirdly creepy Burger King character works well in xBox games, obviously (see yesterday’s headlines). Other products will work in product placements. Others may even work in fiction, who knows. The key here is that in order to achieve Covalence, there must be a tight partnership between advertisers and content producers. Some overall rules may develop here. But initially it’s going to look like a case-by-case creative effort to unearth and execute on Covalence.

It appears that Meredith and Interpublic are realizing the need for closer integration of content creation and advertising. It will be interesting to watch if the product does, in fact, achieve Covalence.