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.

Periodicity

Today during class we discussed the trends that have recently appeared in the organization of the Periodic Table. Using the graphs we created the previous day, we looked at Ionization Energy and Atomic Radius in relation to the elements, and their organization in periods and groups.
1. First Ionization Energy (the difficulty of losing one electron--first level)
--As you move top to bottom in groups, it is easier to lose electrons, therefore the first ionization energy decreases. This is because as you move further down, there are more levels of electron orbitals, and they are easier to loose the farther they are from the nucleus
--As you move left to right in periods, it becomes harder to lose electrons, therfore the first ionization energy increases. This is because as you move across left to right the atomic number increases therefore so do the number of protons, which means there is greater pull on the electrons you are trying to lose.

2. Atomic Radius (size)
--As you move top to bottom in groups, the atomic radii increase. This is because there are more levels surrounding the nucleus, therefore larger atoms
--As you move left to right across the periods, the atomic radii decreases. This is because as you move across periods, the atomic numbers increase, and therefore so do the number of protons in the atom. The greater number of protons, the larger pull on the electron orbitals. The greater the pull on the orbitals, the closer they will be pulled into the nucleus, in turn the atoms will be smaller.

Next Scribe...
Rachel Mann

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.

Light

Hello

Today was a simple class. We just went over the notes.

First we talked about the wavelengths and frequencies of different types of light.

The types of light on the left side of the electro magnetic spectrum have a high frequency and small wave length. The types of light on the right side have a low frequency and a large wavelength.

As the frequency goes up, the wavelength goes down.

Mr. Lieberman used an example. If you are standing on an overpass looking down at two lanes, one of which has semi trucks in it and the other has sports cars in it, the lane with the sports cars will have a higher frequency because more cars can pass by in a given amount of time. The lane with the semi trucks in it will have a lower frequency because less trucks can pass by in a given amount of time, but will have a higher wavelength.
We then took out our cell phones and looked at the infrared light given off through the remote.

Then we learned about the equation for speed which is, wavelength(frequency)=speed.

We aslo learned about Planck. He stated that the transfer of energy is not continuous. His equation for change in energy is: change in energy=hv

h=Planck's constant= 6.626X10^-34 Js

A higher frequency=more energy

A lower frequency= less energy

Einstein stated that electromagnetic radiation was made up of a stream of particles known as photons.

A man named Louis de Broglie connected the two theories about light (that it was in wavelengths or in streams of particles) to make an equation: wavelength=planks constant/mass(velocity)

The last thing we did was put on 3D glasses and look at the lights on the ceiling. We a continous spectrum of light. After that Mr. Lieberman turned on a helium and mercury light and we saw a line spectrum.

Thats we learned about.

The homework is to do the top of the worksheet we got.

The next scribe is Erika

test

it will be monday

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.