Alkenes & Alkynes

• Are unsaturated, therefore containing double or triple carbon bonds.
• General Formula: C_nH_2n and C_nH_2n-2.
• Naming rules similar to Alkanes.
• Endings -ene and -yne are used to name the parent chains in alkenes and alkynes.

Naming Alkenes and Alkynes

1. Finds longest continuous chain of carbon atoms.  Number the carbons by giving the multiple bond the lowest possible number.
2. List and number alkyl groups.  Add prefixes if necessary.  List them alphabetically.
3. Commas used to separate numbers and hyphens are used to separate numbers and letters.

Geometric Isomers

Cis-

Trans-

   

• Labels cis- and trans- are used to distinguish between them.
• Cis- same side
• Trans- across/opposite

Examples:

    

1-hexene

4-methyl-1-pentene

2,3-dimethyl-1-butene

2,3-dimethyl-2-butene

3-methyl-1-butyne

Organic Chemistry

Also known as the Chemistry of Carbon compounds

Some properties :
-have low melting points
-weak or non-electrolytes(put in water and break apart)
-can form chains of C2 atoms that linked in a straight line, circular pattern or branched pattern
-can link other atoms in single/double/triple bonds

Alkanes
-are saturated hydrocarbons which are bonded by single bonds
-hydrocarbons = only hydrogen and carbon thus its not possible for another atom to bond to these structures

For naming, hydrocarbons end with '-ane' just cause :)

Carbon= n
2n+ 2=# of H

Hydrocarbons have side branches which are actually hydrocarbon chains.
Akyl groups- removing a hydrogen atom from an orginal alkane

 this is 4-methyl butane

Naming - replace all '-anes' with 'yls'

If there is more than 1 type of alkyl group, put them in alphabetical order with position number in the front, and put a dash in between alkyl group and number.

Chemical Bonding

There are 3 types of Chemical Bonds :


Ionic bonds which rely on the transfer of electrons
Non polar covalent which rely on the sharing of equal amount of electrons
Polar covalent which rely on the sharing of unequal amount of electrons

Electrostatic Force 
-is a force that exists between charged particles in ionic compounds as a result of Attraction/ Repulsion
-operates equally in all directions

In ionic bonds, a metal and non-metal bonds together. Metals tend to lose electrons due to its low electronegativity values and non-metals gain electrons since they have high electronegativity values.

Electrongativity is calculated by this method :


ENeg Diff. = lENeg1 - ENeg 2l

If ENeg Diff <0.5 it's a non polar covalent bond

If ENeg Diff > 0.5 and <1.8 it's a polar covalent bond

If ENeg Diff > 1.8 it's an ionic bond

In covalent bonds, atoms are held together by intramolecular bonds, they are forces within the molecule and it holds the atoms of the molecule together. These forces are very strong.

However molecules are bonded by intermolecular bonds, which are forces between the molecules itself; they are usually quite weak. In a melting process, only the weak bonds are affected, not the individual molecules.

Polarity

-describes electrical blance of molecule.
-imblance with electrical charge--> polar

-if strength is equal on all sides of molecule--->non polar

Higher electronegativity results in partial negative. (δ- between 0 & -1) Lower electronegativity results in partial positive. (δ+ between 0 & +1) The delta δsymbol represents partial. 

Electron Dot & Lewis Dot Structures

• Picture representation of the valence electron configuration around an atom.
• Valence electrons represented by dots.
• Nucleus represented by atomic symbol.
• Electrons are placed up to two on each side of the symbol for a maximum of eight, which is a full shell.
• A single electron is placed on each side before pairing them.
• Hydrogen and Helium, only a maximum of 2 electrons (exception).
• Lines between atoms indicate chemical bonds.
• Single lines --> single bonds
• Double lines --> double bonds
• Triple lines --> triple bonds
• Hydrogen and Fluorine never go in center "nucleus"
• Metals are in center
• When one element is singled out, it goes in the center.

Octet Rule

Atoms that combine and form bonds either by transferring electrons to form ions or by sharing electrons in covalent bonds until valence shells are full.

• CNOF (Carbon, Nitrogen, Oxygen and Fluorine) always follow octet rule.

Steps to Drawing a Lewis Structure

1)  Pick a Central Atom

• Pick atom with lowest electronegativity
• Central atom: one furthest from obtaining a full shell.
• Connect other atoms with a single bond.
• They might change to double or triple bonds.

2)  Count Electrons

• Only worry about the shells in the outer shells.
• Apply Octet Rule: valence shell must contain 8 electrons to be stable.

3)  Place Electrons around Atoms

• Once you know how many electrons to draw around each atom, place them on structure.
• When lone pairs are placed, find atoms that do not fulfill octet rule.
• There may be double or triple bonds formed 
• **A pair of electrons form a bond.
• Once electrons are placed, put brackets around the entire structure, if there is a charge on the molecule, write it as a subscript on the upper right, outside the brackets.

Examples:

H₂ 

  


_Cl2    
         

H₂O  

        

NH₃
      

CH₄     

      

O2
   
   

N₂    

                          

 NH₄⁺

 

CO₃^2-

 
^{Open circles represent 2 extra electrons from 2- charge.}

Bohr Model

The Bohr model is the diagram we use today to visualize what an atom looks like.

click to enlarge

Orbitals: the space occupied by electrons, also known as shells

This is what Bohr believed:

• Electrons have certain energy levels
• When electrons jump to a different orbital, they release a certain spectrum of light
• Ground states are the lowest energy states
• Excited states are when the electrons jump into a higher or lower level
• Each element gives off a certain spectrum of light when they are heated

We use this to identify what elements are present in distant stars

 

Structure of a Bohr model

Here are the orders of the shells and the maximum electrons they can have

1^st shell: 2 electrons

2^nd shell: 8 electrons             } octet rule

3^rd shell: 8 electrons             }

In the middle of the diagram, we write the atomic number (number of protons) and the number of neutrons

For example:

The atomic number of chlorine is 17. The atomic mass of chlorine is ~35.

To find the number of neutrons we subtract the atomic number from the atomic mass

  35

­-17

 18

So in the middle of the diagram, we write

17p

18n

Periodic Table Trends

This is our current Periodic Table of Elements

Metallic Properties

• Elements on the Periodic Table change from Metal, to Metalloid, to Non-metal as they go from left to right
• Elements become more metallic as the go from top to bottom

Metal

• A solid material that is typically hard, shiny, malleable, fusible, and ductile, with good electrical and thermal conductivity
• Found on the middle and left side of the Periodic Table

Metalloid

• Properties are intermediate between those of metals and solid non-metals
• Are electrical semiconductors

• Found in between metals and non-metals, separating the two like a staircase

Non-metal

• Does not have the properties of metallic elements, such as malleability
• Usually found in nature as gases or weak, brittle solids
• Found on the right side of the Periodic Table

Reactivity

• The ability of atoms of the element to donate, receive, or share electrons with the atoms of another elements
• From left to right, reactivity decreases
• From top to bottom, reactivity increases

Atomic Radius

• The size of the atom
• The distance from the atomic nucleus to the outermost electron orbital
• From left to right, atomic radius decreases
• From top to bottom, atomic radius increases

Density

<insert pic>

• How compact an atom is
• From top to bottom, density increases

Boiling/Melting Point

• The temperature at which an element boils or melts
• Elements at the centre of the periodic table have the highest boiling/melting point

Electronegativity

• The tendency of an atom to attract electrons in the formation of an ionic bond
• From left to right, electronegativity increases
• From top to bottom, electronegativity decreases

Ionization Energy

• The energy needed to remove electrons from the atom
• From left to right, ionization energy increases
• From top to bottom, ionization energy decreases

Ion Charge

• The charge (positive/negative) of an element
• Depends on their groups