Covalent Bonding

Today's topic was covalent bonding. Covalent bonding is bonding between two non metals. In covalent bonding an electron is not lost or gained by an atom or molecule but rather shared between them in bonds. F2 is a very simple example of a covalent bond. They share electrons with each other.

Fluorine only has a single bond. Molecules can have up to triple bonds and can have crazy shapes and patterns depending on what is being bonded and how many are being bonded.

In class we also went over how we can represent covalent bonds in diagrams. One in the pic above is the simpler of the two the other however helps a lot later on when getting into representing bigger molecules. The Lewis Structure.

We got a set of guidelines on how to make a Lewis structure.

1) count the total number of valence electrons and include any ions (+) or (-)

2) Predict the layout of the diagram. First atom listed in the formula is usually in the middle. Just be sure to remember that H can only be bonded to one other atom.

3) Find the number of valence electrons left over from forming the single bonds. Each bond counts as 2 electrons

4) Place the electrons around the outside atoms until each outside atom has 8 electrons around it. Just remember that H follows the duet rule. It only has 2 electrons.

5) Its OK to have more than 8 electrons around the central atom as long as it is the third row or lower on the periodic table. If there isn't enough electrons to put 8 around the central atom then go back and change some of the single bonds to double or triple bonds. C, N, O, and S are commonly know to form double and triple bonds.

Well that about covers everything we went over in class today. HW for today was the Lewis Structure worksheet.

Next scribe is Chris.

Ionic Bonding

Wednesday our class went over ionic bonding. This is the bonding between a metal and a non metal. The main thing in this concept is the Valence electrons. These electrons are what make up the outside energy level.

Ex. 1s22s22p5 The valence electrons for this would be the 2s2 and the 2p5 for a total of 7 valence electrons.

We learned that ionic bonding includes 3 steps: 1) Loss of a e- 2) gain of an e- 3) the atoms or molecules attract.

We also went over how to create a Lewis Diagram as seen on the pic to the right.

The diagram to the right is a lewis diagram of Sodium Chloride. The Sodium wants to get a full energy level and the easiest way to do that is by dropping an electron. The chloride molecule on the other hand wants to get a full energy level by gaining and electron. That is the easiest way for it to get to a full energy level.

That's about all we covered for Wed.

orbital diagrams

today during class we learned how to write the short version of an electron configuration and how to make an orbital diagram. to write a short-hand electron configuration, you write the symbol of the closest noble gas before the element in brackets and then you write the rest of the configuration as normal.

ex: for potassium it would be [Ar] 4s*1

we also learned about orbital diagrams and how to write them. lieberman explained to us how in an orbital diagram you should always write the arrows from left to right and all of the spaces in the sub-level fill up with one first and then you fill the second part when they all have one inside. if you have any questions Mr. Lieberman's email is: dlieberman@glenbrook225.org.

ex. (↑↓) (↑ ) (↑ )

The Next Scribe is...

Bailey M.

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.

Spontaneous reactions, Entropy and Gibb

Hey everyone~

Sorry about not posting yesterday :(

But otherwise, i'll be explaining yesterday and today's day in Chemistry.

On Tuesday, Mr. Liebs explained Spontaneous Reactions and Entropy (\DeltaS).

Although it's all in our notes, I'll just summarize the basic points:

Spontaneous Reactions: a process that takes place on their own, without outside forces

Some examples are...

- ice cubes melting when added to water at room temperature

- mixing hydrogen and oxygen to form water when a spark is applied

- iron rusting because it's exposed to moist air

(These reactions will happen no matter what, in these given conditions)

Entropy

Nature tends to move spontaneously from an orderly state to a random/disorderly state (a process known as the randomness factor).

And connecting with this "randomness" idea is entropy: an increase in disorder or randomness shown as \Delta S

Entropy is highest in this order of states: solid <>

When using entropy in reactions, the equation is \Delta S =\Sigma \Delta S (products) - \Sigma \Delta S (reactions)

Note: when calculating entropy, the coefficients should be a part of the equation (multiplied to each term, accordingly)

On Wednesday, Mr. Liebs continued on with another explanation of notes on Gibb's Free Energy: the energy in the system that is available to do useful work.

A reaction can do useful work if it's spontaneous; and whether or not it's spontaneous can be found through this equation: \Delta G = \Delta H - T \Delta S (as long as temperature and pressure are constant)

Note: In the latter equation, 'T' or temperature has to be in Kelvin)

We will know if the reaction is spontaneous by knowing if \Delta G is a positive or negative value.

If \Delta G is negative, the equation is spontaneous

If \Delta G is positive, the reverse equation is spontaneous

[Look at Table 17.2 in the textbook for more information]

Homework:

Tuesday's homework: Hess' Law Lab

Hess' Law Worksheet

Wednesday's homework: Gibb's Free Energy Worksheet

WebAssign

AND THURSDAY'S TEST WILL BE MOVED TO FRIDAY BECAUSE OF THE SNOW DAY!

So have a fun snow day tomorrow! :)

And the next scribe will be....... Paige H.

Hess's Law Lab

Friday was a pretty simple day in Chemistry. We started off class by going over the procedures for Hess's Law Lab. Here are some tips that might help you with the lab: When you are trying to find the heat of reaction for Reactions 1 and 2 you have to use q=mc∆t. Once you find J, all you have to do is divide that by 1000 to put it into kJ and then divide the kJ by the moles of magnesium/ magnesium oxide used in the experiment. Once you find the heat of reaction for both experiments, use Hess's Law to find the heat of reaction for the combustion of magnesium.

And the next Scribe is Rachel K.

Hess' Law

The class started off today with Liebs showing us the experiment that failed yesterday. He was showing us how the process of sublimation could change to fusion. In order to do so he put frozen carbon dioxide, or dry ice, under "intense" amounts of pressure.

Once the dry ice melted under the water, it would pop under the pressure and send water everywhere, which was terrifying to some of the people in our class... so this is is the same thing, but without the "pop".



Moving onto the lecture today, we spent the rest of class discussing something called Hess' Law. Hess' Law basically says that you can use multiple ways to find Hess' Law, and it will still work, as long as you come to same, correct conclusion.

"If you ski down a hill, it doesn't matter the path you take, you're still going to get to the bottom. As long as you don't hit a tree."

Basically you are given a formula, and you must add and subtract a series of other equations to match it, and then do the same process to series' delta H's in order to find the original missing delta H. To change the equations you can do one of two things: you can flip the formulas around or multiply their coefficients by a number. When adding the equations, if they are on the opposite side of the arrow and the same element/compound they cancel. If they are on the same side then they combine.

An example: