Final Exam Review: #7

To see my answer, click here to see my prezi.

Nuclear Chemistry in conjunction with Cancer Patients

When many people think of a treatment for cancer, their minds immediately jump to chemotherapy.  Although rooted deeply in chemistry concepts, another treatment is very interconnected with nuclear chemistry.  To learn more about this radiation therapy, view my prezi by clicking here.

Molecular geometries that you see everyday!

Everyday items may indeed have shapes similar to the molecular geometries of certain covalent compounds.  Below are some examples:

There are several "linear" objects that we can see in a single day.  A pencil, for example - or even your body when standing straight up.

"Bent" geometries are a bit harder to find.  I noticed that my lamp, which has adjustable joints, can form a stick-and-ball model of a "bent" molecular geometry.

One of the most difficult to find, in my opinion, would definitely have been the "trigonal pyramidal."  I noticed that a foldable stool illustrates the idea of three bonds and one lone pair quite nicely.

If you go driving, you may notice a Mercedes on the streets.  This is where I found an example of the "trigonal planar" geometry.  The logo itself is drawn via connecting the vertices of a triangle inscribed in a circle.

Finally, a "tetrahedrally" shaped item can be easily located by any photographer.  One of their main tools, the tripod, forms this shape almost perfectly.  In fact, when the tripod is un-extended, it could fall under the trigonal pyramidal category.

Attributions:

Linear Geometry Picture:
http://toxicopoeia.com/main/pics/3d_structure_linear.jpg

Pencil:
http://www.wpclipart.com/education/supplies/pencils/pencils_2/wooden_pencil_horizontal.png

Bent Geometry Picture:
http://0.tqn.com/d/chemistry/1/0/8/u/bentgeometry.jpg

Lamp:
http://www.potterybarn.com/products/newbury-halo-task-floor-lamp/?pkey=e%7Clamp%7C86%7Cbest%7C0%7C1%7C24%7C%7C16&cm_src=PRODUCTSEARCH||NoFacet-_-NoFacet-_-NoMerchRules-_-

Trigonal Pyramidal Picture:
http://img.freebase.com/api/trans/image_thumb/m/02fj9jd?errorid=%2Ffreebase%2Fno_image_png&maxheight=200&mode=fit&maxwidth=150

Foldable stool:
http://image.made-in-china.com/2f0j00TutEzhQqjaJk/Aluminium-Foldable-Stool-with-3-Legs-DD2013-.jpg

Trigonal Planar Picture:
http://0.tqn.com/d/chemistry/1/0/6/u/trigonalplanargeometry.jpg

Mercedes Logo:
http://www.smartphotoshop.com/images/merc_14.jpg

Tetrahedral Picture:
http://0.tqn.com/d/chemistry/1/0/B/u/tetrahedralgeometry.jpg

Tripod:
http://www.tnsdistribution.com/aerlingus/ftpimages/large/12.jpg

An Electron-ic Poem

How and why we're shared

To minimize repulsion

And form the octet

Why are covalent bonds formed, you may ask?  Since atoms aim to have the electron configuration like those of the most stable noble gases, said atoms must attain eight valence electrons (except for hydrogen, which only needs two).  By sharing electrons with other atoms (in other words, forming a covalent bond), the atoms can make their orbitals overlap so as to have the eight valence electrons.  The minimization of repulsion is evident in the different molecular geometries that covalent compounds emulate.  For example, in a tetrahedral form (4 bonded pairs, no lone pairs [on the central atom]), the bonded atoms each move 109.5º away from another, ensuring the least amount of repulsion from the electrons possible.  In essence, this haiku states two of the main principles of behavior that are followed by electrons when a covalent compound is formed.

Did I really just swallow that?

On the ingredients list of the now-decipherable Centrum Multivitamin/Multimineral Supplement, I ran into some ionic compounds that were understandable.  All ten listed below were on said ingredients list; it really is a multi-ionic compound supplement!

1) calcium carbonate

2) magnesium oxide

3) potassium chloride

4) cupric [copper (II)] sulfate

5) manganese sulfate

a) manganese (II) sulfate

b) manganese (III) sulfate

6) nickelous [nickel (II)] sulfate

7) zinc oxide

8) stannous [tin (II)] chloride

9) potassium iodide

10) sodium selenate

You can find ten more examples on my partner's blog.  Click here

Test Review: #3

3.  Looking at the trend in first ionization energies across period 3, there is a sudden unusual dip with Al and S.  Explain this.

Well, at first we look at this problem and say what, this doesn't make sense.  Ionization energy is supposed to increase across periods, not drop!  Well, there just so happens to be an anomaly in this all too perfect trend.  To better understand this question, look at the visual display of first IEs below.

Also, to take a look at another representation, click here

Now, what the problem is asking for is this: why does IE drop from Mg to Al and P to S (you can ignore Si)?

Well, the answer in a nutshell is that it is a matter of stability.  Look at the orbital filling diagrams below:

Let's look at the first pair: Mg and Al.  Mg has a completely empty 3p sublevel while Al has a lone electron floating in that same corresponding sublevel.  Mg has added stability because of its completely filled 3s sublevel and it wouldn't benefit the atom if one of those electrons were ripped away.  Taking away an electron from Mg would be ruining the added stability of having a completely filled sublevel.  Al, on the other hand, would benefit from losing an electron because then its 3p sublevel would be completely empty.  An empty sublevel is more stable than one with a single electron roaming around.  That is why, if you steal one of Al's electrons, more stability would be added.  So, because Mg avoids ruining the stability it has and Al aims to get the stability Mg has, there is a dip in IE.

The next pair, P and S, can be explained with the same reasoning.  P has a half-filled 3p sublevel and S has 4 electrons in that same sublevel.  Again its about stability.  P  has already achieved stability by only having 2 electrons in 3 orbitals but S aims to have 3 electrons in 3 orbitals.  So, for the matter of stability again, P avoids ruining its stability while S benefits from gaining P's.  Therefore, there is a dip in IE.

*The easier it is to remove an electron (in other words, the more an atom tries to lose an electron-for stability in this case), the less energy is required to remove it.

Attributions:

The visual display of IE:
http://www.chemguide.co.uk/inorganic/period3/iechart.gif

Second display:
http://www.uwec.edu/boulteje/Boulter103Notes/21October_files/image002.jpg

The Discovery of the Neutron

We have already talked about the discovery of the electron by J. J. Thompson.  However, today, we will be talking about the discovery of the neutron, by James Chadwick.  So I hope you're ready because this is quite the experiment.  Click on the link if you dare to proceed into the world where physics meets chemistry, but first, read what is below:  The Discovery of the Neutron
Click More and then Fullscreen to see the Prezi.  To advance through the slides, press the Play button.
All numbers in parentheses seen near or around something (not in circles, but rather parentheses) are denotations of footnotes.  The citations of these are at the end, in the slide entitled bibliography.