Electron Configurations

So today in class we had quite a long, and somewhat decieving, lecture by Mr. Lieberman.

We learned how to find the electron configurations for neutral elements. The first sublevel s can only hold two electrons, therefore, if the electron is completely filled at this level, the equation would read: 1s^2. The superscript (or exponent) tells you the element. Since the exponent is 2, the element would be Helium. Once a sublevel has been completely filled, if another electron is added, then a new sublevel begins to fill. If this sublevel is completely filled, then the equation would read, 2s^2. Now, this is where it gets tricky. In order to be able to identify the element, you must add this exponent to the exponent in the previous sublevel(s). In this case, 2 from the first sublevel and 2 from the second sublevel gives you 4 electrons. Now you are able to identify the element, which would be Beryllium. Energy sublevels continue to be filled and you add the exponents the same way to find the element.

A further explanation from the book might help you understand this.

1. The elements in groups 1 and 2 on the Periodic Table are filling an s sublevel. Thus, Li and Be in the second period fill the 2s sublevel. Na and Mg in the third period fill the 3s sublevel and so on.


2. The elements in groups 13 through 18 (six elements in each period) fill p sublevels, which have a capacity of six electrons. In the second period, the 2p sublevel starts to fill with B and is completed with Ne. In the third period, the elements Al through Ar fill the 3p sublevel.


3. The transition metals, in the center of the periodic table, fill d sublevels. Remember that a d sublevel can hold ten electrons. In the fourth period, the ten elements Sc through Zn fill the 3d sublevel. In the fifth period, the 4d sublevel is filled by the elements Y through Cd. The ten transition metals in the sixth period fill the 5d sublevel. Elements 103 to 112 in the seventh period are believed to be filling the 6d sublevel.


4. The two sets of 14 elements listed separately at the bottom of the table are filling f siblevels with a principle quantum number two less than the period number. That is... 14 elements in the sixth period (elements 57 to 70) are filling the 4f sublevel.

An example of an equation we did in class is as follows:

1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5p^2 6s^2 4f^14 5d^10 6p^6

The subscripts tell you the energy level, the letters tell you the orbitals, and the exponents (or superscripts), when added together, tell you the electrons. If you were to add all the exponents in this equation, the number would be 86, which is the element Rn (radon).

The next scribe is...

Matt B.

Quantum Numbers

On Thursday we got some new class notes. We talked about the Quantum Mechanical Model and Quantum Numbers.

The Quantum Mechanical Model describes the electronic structure of the atom as the probability of finding electrons within certain regions of space (orbitals). Remember that in the orbital or "electron cloud" there is only about 90% probability of finding an electron within the orbital. Also, according to Heisenberg's Uncertainty Principle, it is impossible to know both the velocity and position of an electron at the same time.

Some things you should know about Quantum Numbers:

• They are used to specify the "address" of each electron in an atom.



• No atom has the exact same quantum number as another atom, they are all unique (refer to the stadium model in the notes).



• There are four quantum numbers:

Principal Quantum Number (n) which is the most general #. It tells us the energy level and sixe of the orbital. Note: These numbers can only have integral values, and the must be positive.

Angular Momentum Quantum # (l) which tells us the enegry sublevel, type of orbital, and shape of orbital (s, p, d, or f). The value of l has integral values from 0 to n-1, and is related to the shape of the orbital. l=0 is s orbital, l=1 is p orbital, l=2 is d orbital, l=3 is f orbital.

Magnetic Quantum Number (ml) tells us the orientation of the orbital, specifies the exact orbital within each sublevel, and has values between l and -l.

Spin Quantum Number (ms) has an electron spin of either -1/2 or +1/2. An orbital can hold two electrons as long as they are spinning in opposite directions.

That pretty much covers what we learned on Thursday. The next scribe is me again, since I forgot to scribe today.

Hey everybody, greetings from Cairo. I promied that I would get our 7th period blog a dot in Africa. The picture is of the pyramids from our hotel room. (Sorry if it's hard to see, it's really dusty and it was early in the morning).

Hey guys,
Greetings from London!!!!!!! I put a new dot on the map in Europe, and I'm headed off to Cairo today, so look for a new dot on the map there. Hope you are all enjoying your break.

Balancing Equations and Chemical Reactions

Today we began our discussion on the balancing of equations. One of the most important things to remember as you balance a chemical equation is the Law of Conservation of Mass, or in other words, what you start with you have to end up with. When dealing with an equation, you may only change the coefficients, NOT the subscripts. Two things you can do when balancing an equation is first: to start simplifying the atoms that only appear once in the formula, and second: to always balance and oxygen last.

There are five types of chemical reactions. The two we began discussing in class today were:

1. Synthesis reactions. These types of reactions occur when two substances (generally elements) combine and form a compound. Reactant + Reactant --> 1 product or A + B --> AB. An example of a synthesis reaction is 2 H2 + O2 --> 2 H2O

2. Decomposition reactions. This kind of reaction occurs when a compound breaks up into the elements or in a few to simpler compounds. 1 reactant --> product + product or AB --> A + B. An example of this type of reaction is 2 H2O --> 2 H2 + O2

In order to further explain these two reactions, Mr. Lieberman showed us two demonstrations.
http://www.youtube.com/watch?v=8ncN7AdROrY

The first video demonstrates a synthesis reaction. Liebs used a balloon filled with hydrogen gas and a candle as the two reactants. When the open flame touched the candle, it reacted violently with the hydrogen inside the balloon, causing the balloon to pop (although it was more of an explosion) and the product of the reaction was water.

The second video shows an example of a decomposition reaction. A large graduated cylinder was filled with hydrogen peroxide and some dish soap. When Liebs added the catalyst, the hydrogen peroxide reacted and foamed over the top of the graduated cylinder. Liebs calls this demonstration "elephant toothpaste."
http://www.youtube.com/watch?v=f_ftXxCwvDw

So that pretty much sums up what we learned in class today. Sorry everybody, my computer won't let me upload/embed the videos, so I just posted the web addresses to each of the videos. Hopefully they work.
Also, the next scribe is................. Nirali P.