May 30 2011 - Alkenes and Alkynes

Me: Today we learned about alkenes and alkynes.

Billy: Why did you say alkanes two times?

Me: No, I said alkenes and alkynes.

Billy: You just did it again.

Me: No I di- nevermind let me explain

Alkenes are is the simplest of the unsaturated hydrocarbons, hydrocarbons which will react with hydrogen.  They contain one or more double bonds between carbon atoms.  They are indicated by the symbol =.  The presence of a double bond is indicated when the ending changes from -ane to -ene.   The formula for alkenes is C_nH_2n.

Alkenes
Ethene	C2H4
Propene	C3H6
Butene	C4H8
Pentene	C5H10

 Alkynes are hydrocarbons which contain a triple carbon bond.  They are indicated by a symbol of 3 lines.  The presence of a triple bond is indicated when the ending changes from -ane to -yne.  The formula for alkynes is C_nH_2n-2.

Alkynes
Ethyne	C2H2
Propyne	C3H4
Butyne	C4H6
Pentyne	C5H8

                                                                         
Trans and Cis
Are these two molecules the same?  No they are not because no matter how you rotate the molecule, you do not end up with the same molecule.  One of these is cis and one of these is trans. Which one is which?  The one on the LEFT is trans, because the methyl groups are on the opposite ends. The one on the right is a cis, because the methyl- groups are located on the same side. The molecule on the left is called trans-2-butene, while the right one is called cis-2-butene.
           *note* this only applies to alkenes        



Ohhhh yeah 2 weeks left.  Enjoy the vid.

May 26 2011 - Organic Chemistry: Alkanes

Organic chemistry, what is that and what do we need it for?  Organic chemistry is a subsection of chemistry involving the scientific study of the structure, properties, composition, reactions, and preparations of carbon-based compounds, hydrocarbons, their derivatives.  It is what created many of the everyday products that we use.


Organic compounds have low melting points, non-electrolytes and form chains in straight lines, circular patterns or branched patterns.  These can be linked up in single, double or triple bonds.


Alkanes are saturated hydrocarbons where all the bonds are single bonds.  Each carbon atom forms four bonds and each hydrogen forms a single bond to a carbon.  The bonds are tetrahedral which form an angle of 109.5 deg.  

Selected Properties of the First 10 Normal Alkanes
Name	Formula	Molar Masses	Melting Point (°C)	Boiling Point (°C)	Number of Structural Isomers
Methane	CH4	16	–183	–162	1
Ethane	C2H6	30	–183	–89	1
Propane	C3H8	44	–187	–42	1
Butane	C4H10	58	–138	0	2
Pentane	C5H12	72	–130	36	3
Hexane	C6H14	86	–95	68	5
Heptane	C7H16	100	–91	98	9
Octane	C8H18	114	–57	126	18
Nonane	C9H20	128	–54	151	35
Decane	C10H22	142	–30	174	75

Formula for writing alkanes:  C_nH_2n+2.  Where n = number of carbon atoms.


Hydrocarbons can also have side branches.  Branched hydrocarbons are hydrocarbon molecules where the carbon atoms are not arranged in a simple chain, but are arranged in a network of multiple chains. 


Naming branched hydrocarbons

Substituent Formula	Number of C Atoms	Name of Substituent
CH3	1	methyl-
CH3CH2	2	ethyl-
CH3CH2CH2	3	propyl-
CH3CH2CH2CH2	4	butyl-
CH3CH2CH2CH2CH2	5	pentyl-

1. Find and name the longest continuous carbon chain and place it at the end of the name.
2. Identify and name the groups attached to the chain
3. Number the chain, starting at the side nearest to the side group
4. Designate the location of each side group by an appropriate number and name
5. Assemble the name, listing groups in alphabetical order.

What a loser...puts part 2 and 3 on his website to force you to go there.  Well ha! only watch his vids on youtube.

May 18 2011 - Electronegativity and Polarity

It's the long weekend and my parents are on my tail about not doing any work, so here I am!  So lets see...what did we learn this class,OMGWTFBBQ.  What is this this thing called electronegativity and polarity.

Electronegativity is a measure of attraction of an atom for electrons in a covalent bond.  When 2 different atoms are covalently bonded, they share electrons.  This type of bond is polar.  Polar bonds result in unequal sharing of electrons in bonds.

Bond types
The difference in electronegativities of 2 elements can be used to predict the natures of bonds.  Bonds are categorized into 3 classes:

1. nonpolar covalent - electrons are shared equally between two atoms
2. polar covalent - one atom has a greater attraction for electrons than the other atom
3. ionic - bonding electrons are given away completely to one of the bonding atoms

Predicting Bond Types
When differences are less than 0.5, bonds are considered nonpolar.  (0-.04)
When differences are less than 1.7 and greater than 0.5, the bond is covalent.  (0.5-1.7)
When differences are 1.7 or greater, the bond is ionic
(1..7 and up)
*wait waaah?? shouldnt it be 1.8? N O.  I looked and I kept seeing 1.7 so get over it. *




Eg.
What type of bond will HCL be?
H has an electronegativity value of 2.10
CL has an electronegativity value of 3.16

Difference is: 3.16-2.10 = 1.06

ANSWER: Polar covalent bond  <------


hehe time for a hard one!!!!!
What type of bond will HF be?
H has an electronegativity value of 2.1
F has an electronegativity value of 4.0

Difference is: 4.0-2.1 = 1.9

ANSWER: get ready for this because whatever you got is wrong.  Its a POLAR COVALENT BOND.


Say whaaa???  How is it polar covalent.  Its an exception DEAL WITH IT.


This guy man, hes crazy but hes good.  Enjoy ^_^

May 16 2011 - Bohr Diagram

ARE YOU READY FOR THIS?!?!  Well im not.  Which is why im doing this this blog in the first place.  Its time for the Bohr Model.  Yeah I know right?  This stuff is getting boring but we are almost done.  Just 8 more classes, just 8 more classes.

Niels Bohr proposed the Bohr Model in 1915.  It is a planetary model where negatively-charged electrons orbit the nucleus.  These electrons exist in orbitals and when energy is absorbed, they move to a higher orbital.  When energy is lost, electrons fall to a lower orbital.  

The Bohr diagrams places the number of neutrons and protons in the center and electrons in energy rings around the outside. Each energy ring has a maximum number it can hold

                     Ring 1 – 2 electrons

                     Ring 2 – 8 electrons

                     Ring 3 – 8 electrons

                     Ring 4 – 18 electrons

                     Ring 5 – 18 electrons

                     Ring 6 – 32 electrons

                     Ring 7 – 32 electrons

Drawing Bohr Diagrams

Lithium - two of its 3 electrons go into the first level.  the third electron goes into the second energy level.  

1. Draw a circle and write Li inside of the circle

2. Write the number of protons and neutrons in the circle , which is  3P and 4N

3. Draw an arc which represents the first energy level and label it 2e^-.  This will represent the 2 electrons 

    in this energy level.

4. Draw a second arc which represents the second energy level and label it 1e^- .  This represents the third electron.

May 10 2011 - Lewis Structures

These will help you on the Lewis structures that were learned in class. 


How To Draw Lewis Structures

1)    Count the total valence electrons for the molecule: To do this, find the number of valence electrons for each atom in the molecule, and add them up.

2)    Figure out how many octet electrons the molecule should have, using the octet rule: The octet rule tells us that all atoms want eight valence electrons (except for hydrogen, which wants only two), so they can be like the nearest noble gas. Use the octet rule to figure out how many electrons each atom in the molecule should have, and add them up.  The only weird element is boron - it wants six electrons.

3)    Subtract the valence electrons from octet electrons: Or, in other words, subtract the number you found in #1 above from the number you found in #2 above. The answer you get will be equal to the number of bonding electrons in the molecule.

4)    Divide the number of bonding electrons by two: Remember, because every bond has two electrons, the number of bonds in the molecule will be equal to the number of bonding electrons divided by two.

5)    Draw an arrangement of the atoms for the molecule that contains the number of bonds you found in #4 above: Some handy rules to remember are these:

• Hydrogen and the halogens bond once.
• The family oxygen is in bonds twice.
• The family nitrogen is in bonds three times.  So does boron.
• The family carbon is in bonds four times.

A good thing to do is to bond all the atoms together by single bonds, and then add the multiple bonds until the rules above are followed.

6)    Find the number of lone pair (nonbonding) electrons by subtracting the bonding electrons (#3 above) from the valence electrons (#1 above). Arrange these around the atoms until all of them satisfy the octet rule: Remember, ALL elements EXCEPT hydrogen want eight electrons around them, total. Hydrogen only wants two electrons.

eg.  Draw the lewis diagram for 

CO₂ 

1) The number of valence electrons is 16. (Carbon has four electrons, and each of the oxygens have six, for a total of 4 + 12 = 16 electrons).

2) The number of octet electrons is equal to 24. (Carbon wants eight electrons, and each of the oxygens want eight electrons, for a total of 8+16 = 24 electrons).

3) The number of bonding electrons is equal to the octet electrons minus the valence electrons, or 8.

4) The number of bonds is equal to the number of bonding electrons divided by two, because there are two electrons per bond. As a result, in CO2, the number of bonds is equal to 4. (Because 8/2 is 4).

5) If we arrange the molecule so that the atoms are held together by four bonds, we find that the only way to do it so that we get the following pattern: O=C=O, where carbon is double-bonded to both oxygen atoms.

6) The number of nonbonding electrons is equal to the number of valence electrons (from #1) minus the number of bonding electrons (from #3), which in our case equals 16 - 8, or 8. Looking at our structure, we see that carbon already has eight electrons around it. Each oxygen, though, only has four electrons around it. To complete the picture, each oxygen needs to have two sets of nonbonding electrons, as in this Lewis structure:

Please note: This video IS super interesting and is ALSO very helpful

(Done by Wes, edited by B.W.)   (=   ****   =)

April 20 2011- Electron Configuration

Herrroooooo.  You guessed it its me again Wes.  So about electron configuration...you can do it the bottom, boring, lame super duper hard way.  Or you can do it the easy way in the video at the bottom, your choice really.  Cheers.


So the first way, which is lame in my opinion is, you write then how the arrows go down.  So you start with 1s then 2s then 2p then 3s then 3p then 4s and so on.  Remember this: the maximum amount of electrons in each shell are 2 for s, 6 for p, 10 for d, and 14 for f. 

This way is easier since its more visual.

April 18 2011 - Atomic Mass and Isotopes

Heeeeeeeeeeeey everybody, its me the one and only, Wes here talking about atomic mass and isotopes.  WARNING: you are about to hit a big wall of text.   



                              One way scientists measure the size of something is by its mass. Scientists can even measure very, very tiny things like atoms. One measure of the size of an atom is its "atomic mass". Almost all of the mass of an atom (more than 99%) is in its nucles, so "atomic mass" is pretty much a measure of the size of the nucleus of an atom.  The nucleus of an atom is made up of protons and neutrons. Protons and neutrons are almost exactly the same size. If you add up the number of protons and neutrons in the nucleus of an atom, you get that atom's atomic mass. A simple hydrogen atom has just one proton and zero neutrons. Its atomic mass is 1. The most common kind of carbon atom has 6 neutrons and 6 protons. It has an atomic mass of 12.  All atoms of a certain element have the same number of protons. Oxygen atoms always have 8 protons; carbon atoms all have 6 protons. Most atoms come in different types called isotopes. Isotopes have different numbers of neutrons. The most common isotope of carbon has 6 neutrons and 6 protons. Its atomic mass is 12. A rare,radioactive isotope of carbon has 8 neutrons. Its atomic mass is 14 ( = 6 protons + 8 neutrons).  In chemistry, the number of protons in an atom is more important than the number of neutrons. Scientists call the number of protons the "atomic number". Normal atoms have the same number of electrons as protons. The number of electrons is the main thing that controls how atoms behave in chemical reactions. Scientists use the letter "Z" to stand for atomic number and the letter "A" to stand for atomic mass.

Atoms of the same element can have different numbers of neutrons; the different possible versions of each element are called isotopes. For example, the most common isotope of hydrogen has no neutrons at all; there's also a hydrogen isotope called deuterium, with one neutron, and another, tritium, with two neutrons. If you want to refer to a certain isotope, you write it like this: ^AX_Z. Here X is the chemical symbol for the element, Z is the atomic number, and A is the number of neutrons and protons combined, called the mass number. For instance, ordinary hydrogen is written ¹H₁, deuterium is²H₁, and tritium is ³H₁. Now elements can only have a certain number of isotopes.  there are "preferred" combinations of neutrons and protons, at which the forces holding nuclei together seem to balance best. Light elements tend to have about as many neutrons as protons; heavy elements apparently need more neutrons than protons in order to stick together. Atoms with a few too many neutrons, or not quite enough, can sometimes exist for a while, but they're unstable


VIDEO TIME!!!!!