Monday, May 30, 2011

Alkenes and Alkynes

It's another part of the organic chemistry we have learned in chapter 23. Alkenes and Alkynes are double bonds and triple bonds respectively. The carbon can form bouble and triple bonds with Carbon atoms. When multiple bonds form fewer hydrogens are attached to the Carbon atom.

The naming rules are almost the same as the Alkanes: the postion of the double or triple bonds always has the lowest number and is put in front of the parent chain.

ALKENES
Hydrocarbons with one or more double bonds located between carbon atoms leading to an "unsaturated" hydrocarbon. The ending of a formula is changed from -ane to -ene (for alkenes).



GEOMETRIC ISOMERS : we give the double bonds formula each a different name based on their geometry.


Example:
Cis-2-butene
trans-2-butene




ALKYNES: hydrocarbons with one or more triple bonds located between carbon atoms leading to an "unsatrated" hydrocarbon.

Naming: the ending is changed fron -ane to -yne for alkynes.

Example: 

Thursday, May 26, 2011

Organic Chemistry: The Chemistry of Carbon Compounds

One of the most important element to sustain life is to have the element of carbon (C) in substances like sugar, plants, and us, human. We cannot live without carbon. Organic chemistry is responsible for many of the every-day products that are used around the world.

Properties of Organic Compounds:
  • low melting point
  • weak or non-electrolytes
  • can for chains of carbon atoms that are links in a straight-line, circular pattern and branched pattern.
  • Can like with other atoms in...
    • Single Bonds
    • Double Bonds
    • Triple Bonds


Then, here come a newer stuff, Alkanes, a unbranched/straight chain. For example, a hydrocarbon is a compound that contains only hydrogen and carbon. There are different types of hydrocarbons and there are different ways to represent them. Non-polar nolecules are immiscrible with water, which means they are non-dissolvable.
Here is a 3D modle of a tetrahdron:

Alkanes are saturated hydeocarbon which have all carbon atoms bonded by single bonds. Saturated means that it is not possible for another atom to bond to the structure. Naming of alkanes: the names of all hydrocarbons end in '-ane' because they are 'alkanes'!!!

Examples would be:

Easy to memorize, huh? Ofcourse it is!

Then we had learned about the branched hydrocarbons. Hydrocarbons can have "side branches" with are also hydrocarbon chains: These hydrocarbons are call substitured hydrocarbons or brached hydrocarbons.
Examples would be like:
Naming: the ames of all alkyl groups end in '-yl' bcause they are alkyl
Pentane C5H12       Pentyl C5H12
Butane C4H10        Butyl C4H10
Propane C3H8        Propyl C3H8
Ethane C2H6           Ethyl C2H6
Methane CH4          Methyl CH4

Rules of alkane nomenclature:
1. Find and name the longest continuous carbon chain
and place at the end of the name
2. Identify and name groups attached to this chain.
3. Number the chain consecutively, starting at the end
nearest a side group. (i.e. the lowest numbered carbon)
4. Designate the location of each side group by an
appropriate number and name.
5. Assemble the name, listing groups in alphabetical
order.

Tuesday, May 10, 2011

Electron Dot and Lewis Diagrams

It's very easy to draw a electron dot diagram and a Lewis Diagram. They are both about the same. Just for the Lewis Diagram, the electrons that are bonded between elements are a straight line, instead of a paired electron dot.

The nucleus is represented by the atomic symbol. For individual elements determine the number of Valence electrons. Electrons are represented by dos around the symbol. Four orbitals (one of each side of the nucleus) each holding a maximum of 2 e- (recall: maximum of 2 electrons perorbital). Each orbial gets 1 e- before they pair up.
The dots are placed in 4 groups of one or two electrons, with 8 electrons representing a closed shell or noble gas configuration. The dots are placed on the 4 sides in pairs as a reminder that electrons are paired in the orbitals.



Here are some practise problems from the internet:

Monday, May 2, 2011

Periodic Table Trend

              Today in class, we learned about the Periodic Trends.  The trends tells us the ralationship between elements on the table.  For example there are eight important trends we need to now.  There is the Metallic Properites trend, Atomic Radius trend, Ionization energy trend, electronegativity trend, reactivity trend, ion charge trend, melting/boiling point trend and the density trend.

Metallic properties trend
-elements tend to be more metallic in nature toward the left side of the periodic table
-metallic properties like malleability are result of the little valance electrons
-usally low ionization energies
-elements more metallic to the left side of the stair case
-elements more metallic when down a group

Atomic Radius Trend
-radius decreases when reading down from a group
-radius increases when reading from left to right of a row
-elements have higher enegy level at the bottom.  The atom is more sprend apart making the radius bigger
-elements atomic radius decreases from left to right of the row because the atomic number increases making the nucleaus more attractive to the other electrons.  Thus the atom is more packed together and not wide apart

Ionization of energy trend
-is the process of removing one or more elctrons from an atom to produce an ion
-opposite trend of atomic radius
-energy becomes bigger from left to right of the row because the atom is more tightly packed since the   electrons are attracted to the positve nucleuas with protons.  Thus harder to remove an electron from the atom
-energy decreases as reading down the group because electrons more far apart because of higher energy level. Thus electrons are easier to be remove and requir less energy

Electronegativity trend
-is the ability to attract electons from a neighbouring atom
-same trend as ionization energy
-elements to the right of the row has high ionization energy.  Thus they have higher attraction to their neighbors
-elements down a group has lower ionization energy since their atom is not tightly packed together.  Thus they are loose and will not have enough energy to attract their neighbors

Reactivity Trend
-is how readily an element will react with other elements
-the reacticity trend for metals is different from non metals.  For example when you read down the alkaline metal group the ionization energy decreases.  Therefore it is easier for the element to loos its valace electron and that will make the element more reactive
-for non metals, they tend to want to again electrons.  As you read upward the halogen group the element becomes more reactive since its got higher ionization level.  This means that elements have a lower tendency to lose electrons and a greated tendency to gain them.  Thus elemts become more reactive as you proceed up the group for non metals

Ion Charge
-Elements ion charges depend on thier group

Melting point/boiling point trend
-is the temperature at which it changes from solid to a liquid
-melting point of a substance depends the stregh of their bond.  If the bond is weak the melting point iwll be lower
-melting point for metals usually decreases as read down a group
-melting point for metals usually increases when moving to the right of the row until it reach the middle
-for the halogen group and the noble gas group, the melting point increases as read down the group
-element at the center of the circle has the highest melting point


Photobucket





Density
-The density usually increase by the atomic number