Tuesday, May 31, 2011


Hi all,
as you may recall, last blog we talked about the wonderful world of alkanes. But it was a little plain, no? Now you have the chance to spice it up a little bit with adding in a few doubles bonds here, and a few triple bonds there. Let's start off with a few definitions:
Alkene: An organic compound containing a double bond between two carbons.
Alkyne: An organic compound containing a triple bond between two carbons.
Now we've established the difference between those two, we can get down to business.

Ethylene2.png This is an alkene. Note the double bond.

How to name alkenes? You would name it just like alkanes, except changing the -ane to a -ene. For example, in the above image, there are two carbons. If you were writing an alkane, it would be ETHANE. However, because of the double bond, it is an alkene. Thus, the name for the above compound would be ETHENE.

Drawing them is a different matter. "How would we know where the double bond goes?", you may ask. Here is a better example to work with than the above:

HEXENE.gif Meet hexene. As you can see, his double bond is in the middle of the schmongle. Recall how to write alkanes. Note that the carbon with the double bond is the 3rd one from the left/right. So we wouldn't have to bother with worrying about the smallest number. Since the double bond is on the 3rd carbon, we would name this 3-hexene. So drawing them would be the same matter. Just the corresponding number to where the double or triple bond is.
ethyne.gif Now meet ethyne. Ethyne is an alkyne. How do we know? See that triple bond there basking in it's glory? That's how we know.

Dealing with alkynes may look exhausting because of the triple bond, but do not fear. You'd be glad to hear that you do exactly what you've been doing all along with alkanes and alkenes. Just always, ALWAYS, remember to label where the triple bond is.

TMFAQ (The Most Frequently Asked Question)
Promising title isn't it? But the question is: What if we have a branch AND a double/triple bond?! What do I do with the naming? Would the branch be a priority for the "lowest number" used in describing the compound or would I use the location of the double/triple bond and then do things accordingly?! SAY WHAT?
Calm down, my young disciples. If something looked like this: 
2methyl3hexene.JPG.jpgYou will ALWAYS, prioritize the double bond first. Same with triple bonds (alkynes). THEN, you do things accordingly. Therefore, this would be 2-methyl-3-hexene. 

OChemAthiesm.jpg Calvin's take on "OChem"...

Thursday, May 26, 2011

Organic Chemistry!!! Chemistry that is healthy for you.

Today we are going to learn about ORGANIC CHEMISTRY. Excited? I think so.

Let's review exactly what organic chemistry is:

  • The chemistry of carbon compounds
  • Responsible for many everyday products like: your clothing, plastic, and alcohol
  • Low melting points
  • Weak or No-electrolytes
Types of Carbon Atom Chains
  • A straight-line 
  •   a circular pattern
  •  a branched pattern
Types of Links with Other Atoms
 single bonds
 double bonds
 triple bonds

Moving on, a hydrocarbon is a compound containing only hydrogen and carbon.
Hydrocarbons come in different types and can be represented in different ways. 

Alkanes are saturated hydrocarbon where carbon atoms are bonded by single bonds.
(saturated: atoms cannot bond to the structure)

When naming Alkanes: The names of all hydrocarbons end in "ane"
This is a table of the main alkanes and their chemical formulas:

This table above is a homologous series.
Homologous Series: A series of organic compounds with similar general formulas and chemical properties


Some hydrocarbons are called substituted hydrocarbons or branched hydrocarbons because they are attached to the side of the original hydrocarbon

Now let's move on to Alkyl Groups.
An Alkyl Group is an alkane which lost one hydrogen atom

The names of all alkyl groups end in '-yl'
For example: Propane -> Propyl
With more of the same kind of alkyl group, the prefixes "di, tri, tetra, etc" come in to play
List the different groups alphabetically, ex/ Ethyl is before Methyl
Put the position number in front, and a dash between each alkyl group and it's number

To better understand the naming of Alkyl Groups, click this link:

Monday, May 16, 2011

New Chemical Bonds that will Blow Your Mind!!!!

Recently in Ms. Chen's class, we have learned new types of chemical bonds that I have never dealt with before! They are:

  1. Non Polar Covalent Bonds: if electrons are shared equally
  2. Covalent Bonds: if electrons are shared unequally
  3. Ionic Bonds: if the electrons are transferred between 2 atoms
Before I get into explaining, let's review the basics of Electrostatic Force:
Electrostatic Force is a force that exists between charged particles as a result of attraction/repulsion. This operates equally in all directions.
  • Opposite charges attract
  • Like charges repel
  • The greater the distance between two charged particles, the smaller the attractive force
  • The greater charge on the particles, the greater the force of attraction

Typically, atoms with higher electro negativity strongly attract electrons from neighboring atoms. 

The trends for Electronegativity are the same as the trends for Ionization.
This is because, metals have low electronegativity and non metals have high electronegativity resulting in high ionization energies

You can measure electronegativity using the "Pauling Scale"
Electronegativity Difference = [Energy1 - Energy2]
1) IF ENeg Diff. < 0.5 it is a COVALENT BOND
2) IF ENeg Diff. > 0.5 and < 1.8 it is a POLAR COVALENT BOND
3) IF ENeg Diff. > 1.8 it is an IONIC BOND

NOW we will move on to intermolecular forces. These hold together individual molecules containing intramolecular covalent bonds forming covalent compounds.

How to differentiate between the two?
INTRAmolecular forces are found within a molecule, responsible for holding the atoms of a molecule together
INTERmolecular forces are found between the molecules, responsible for the bonding between molecules

Now you may ask, why do some bonds have low melting points? Well the answer to that question is simply because of weak bonds
                - During the melting process, only the weak bonds are affected. The covalent bonds 
                  within each individual molecule are not broken.
The LONDON FORCES are the weakest intermolecular force. This is due to temporary dipolar attractions between neighbouring atoms

A dipole is a partial separation of charge, existing when one end of a molecule has a slight positive charge and the other end has a slight negative charge

 > Outlines a molecule's electrical balance
 > If there is an imbalance with electrical charge, then the molecule is polar, if it is balanced, it is 
    non polar

Atoms with Higher Electronegativity will form a PARTIAL NEGATIVE charge
δ- (between 0 and -1)
Atoms with Lower Electronegativity will form a PARTIAL POSITIVE charge
δ+(between 0 and +1)

Example: NH3
N: 3.04
H: 2.20

3.04-2.20 = 0.84 meaning it is a polar covalent bond

Here are videos to sum up everything in this blog: 

Sunday, May 15, 2011

Taking Representing Compounds in Diagrams to a Whole. New. Level. ELECTRON DOT AND LEWIS DIAGRAMS

Helloooo readers.

It is now time to take the next step in your relationship with compounds and represent them in what is called "Electron Dot and Lewis" Diagrams. YESS!! -insert confetti-

Now you must be asking how would you ever represent them in that way? Well I will start off by explaining exactly what a Lewis Diagram is.

A Lewis Dot Diagram is a diagram that shows the bonding between atoms of a molecule and the lone valence pairs in the molecule.

  • The symbol of the element is in the center, and electrons are represented by dots surrounding it
  • In total, there are 4 orbitals surrounding the element, each holding a maximum of 2 electrons
  • 8 electrons represents a "closed shell" or "noble gas" configuration
Example Time!!!

Let's show the Lewis Diagram of Chlorine. 
Chlorine has 7 valence electrons, therefore in the Lewis Diagram, there are 3 full orbitals and 1 half full orbital

These are the Lewis Diagrams for part of the Periodic Table

Now let's do an example of a Lewis Dot Diagram for a compound

-In order to complete it's outer shell to make it contain 8 valence electrons, atoms gain, lose, or share electrons
-Carbon, Nitrogen, Oxygen, and Fluorine always follow this rule
  • In this case, Nitrogen needed 3 electrons, and fluorine only needs 1 electron, therefore, nitrogen shares 3 bonds with 3 fluorines

Now, this is the Structural form of NF3


This is a video to help you further understand the Lewis Dot Diagrams:

Monday, May 2, 2011

Periodic Table Trends

There are many trends that can be identified on the periodic table of elements. The ones that we will be reviewing today include:

  • Metallic Properties
  • Atomic Radius
  • Ionization Energy
  • Electronegativity
  • Reactivity
  • Ion Charge
  • Melting/Boiling Point
  • Density

Density: Elements become more dense as we reach the middle of the periodic table.

Metallic Properties: Elements go from metallic -> non-metallic as we go from left to right on the periodic table. Elements at the bottom of a group are more metallic than those at the top of the group. 

Melting/Boiling Point: Elements at towards the centre of the table have the highest boiling points. Noble gases have the lowest melting point. 

Ionization Energy: This is the energy required to remove one electron from a neutral atom. This trend increases upwards towards to right of the periodic table. Meaning that helium has the highest ionization (holding tightly onto its electrons because it has a perfect full shell) energy, and francium has the lowest (eager to get rid of its one valence electron). Ionization energy is given in kj/mol.  

Electronegativity: This is basically a way of saying how much an atom wants to gain electrons. Noble gases are excluded from this trend because they already have a full valence shell, and therefore do not need to gain or lose any electrons. 

The trend of electronegativity is basically the same as ionization energy. So it goes up and to the right. Fluorine is the most electronegative element. 

High electronegativity: This atom strongly attracts neighbouring electrons, and may quite possibly even remove it. At the same time this atom holds tightly onto its own electrons. 

Low electronegativity: This element doesn't attract neighbouring electrons very well, in fact, it even allows its own electrons to be easily removed. 

Atomic Radius: The atomic radius decreases as we move towards to right side of the periodic table. Reason being that there are more protons and electrons, causing more attraction, which packs the atom together more tightly. The atomic radius increases down a group, because as you go downwards, the elements atoms have more shells which make the atom larger. 

Reactivity: Atoms that are closer to getting a full valence shell (by either gaining or losing electrons) tend to be more reactive. Noble gases are very stable because they already have a full shell.