Our first book will be:

We'll be holding the Google hangout during the first week of August (date and time depending on who wants to participate and their availability).

Please share this! 

I think it would be awesome to have a big group of people discussing #SciBook.

No, the warning I'm talking about is much more simple. Here it is:

That's it. The only warning is: "Phenylketonurics: Contains Phenylalanine". What does this warning mean? Well, to tell you the truth if I have to explain what this warning means then it doesn't apply to you. 

You see, there is a specific genetic defect, called phenylketonuria, which (in short) messes with your liver and makes it impossible to correctly digest phenylalanine, a common amino acid. Phenylalaine is an essential amino acid that is used by your body to synthesize dopamine, a necessary neurotransmitter. An excess of phenylalanine, like you would see in phenylketonuria, can lead to serious problems including mental retardation and death. Phenylketonurics (those that suffer from phenylketonuria) must live on a diet that restricts intake of phenylalanine. Therefore, the warning is placed on diet sodas. 

But some would argue that if it's really bad for some people we should all avoid it. If the warning that diet soda contains phenylalanine prompts you to avoid phenylalanine, here's a list of other foods you should also avoid, as they also contain phenylalanine (and some in much higher doses):

I've been teaching general chemistry concepts for several years now. For some reason the idea of atomic orbitals is hard for students to grasp. Tonight I'm holding an exam review for my students and I thought I'd prepare by writing about the quantum numbers and how they affect the shape of atomic orbitals.

The Quantum Numbers

n: The principal quantum number. n can be any positive integer (1,2,3,4...)

0 = s
1 = p
2 = d
3 = f

There are two other quantum numbers, but we aren't concerned with those for this exercise.

Nodes
In quantum mechanics a node is a point where an electron cannot exist. The shape of any orbital is defined by the nodes. There are two types of nodes: angular and radial.

Angular: An atomic orbital will have l angular nodes. So, an s-orbital has 0 a p-orbital has 1, and so on.
Radial: Each atomic orbital will have n-l-1 radial nodes. So a 3p orbital has 3-1-1 = 1 radial node.

Drawing orbitals
Ok, so what you've read above is explained in just about every general chemistry textbook. But, when asked to draw orbitals most chemists just pull from memory. You don't need to do that, though. You don't have to memorize the shape of a single atomic orbital. You just need to know understand the quantum numbers. Let's start with 1s.

1s
Angular nodes: 0
Radial nodes: 0

This is the easiest. We'll always start with a circle. There are zero nodes and so we're already done. We'll say that 1s looks like this:



Moving on...

2p
Angular nodes: 1
Radial nodes: 0

We start with the same circle, but this time we need to add an angular node.

 Which, once you smooth the edges looks just like the actual 2p orbital:


 Let's do the 3d orbital now

3d
Angular nodes: 2
Radial nodes: 0


Which, after we smooth out the edges, is a pretty good prediction:




 The great thing about drawing the atomic orbitals this way is you never have to memorize any of these shapes - they come directly from understanding what the quantum numbers mean.

Now, if you're one of my students, get back to studying.

Notes

All of the "real" atomic orbitals from above were created using Orbital Viewer, a very cool (and free) program.