Alkenes and Alkynes

There are unsaturated hydrocarbon compounds that are either connected by double bond or triple bond.  Alkenes are the ones bonded by a double bond and alkynes are the ones bonded by a triple bond.  For alkenes the root names give the number of carbons in the longest continuous chain. Alkene names are formed by dropping the "ane" and replacing it with "ene".  It is written with this formula: C_nH_2n.  For alkynes the root names give the number of carbons in the longest continuous chain. Alkyne names are formed by dropping the "ane" and replacing it with "yne".  It is written with this formula: C_nH_2n-2.

A table for alkenes:

No. of Carbons	Root Name	Formula CnH2n	Structure
2	ethene	C2H4	CH2=CH2
3	propene	C3H6	CH2=CHCH3
4	1-butene	C4H8	CH2=CHCH2CH3
5	1-pentene	C5H10	CH2=CHCH2CH2CH3

A table for alkynes:

No. of Carbons	Root Name	Formula CnH2n-2	Structure
2	ethene	C2H2	CH=CH
3	propene	C3H4	CH=CHCH3
4	1-butene	C4H6	CH=CCH2CH3
5	1-pentene	C5H8	CH=CCH2CH2CH3

Here is a video explaining name both alkenes and alkynes:

Alkanes

Alkanes are chemical compounds composing of only carbon and hydrogen atoms by single bonds.  The image above is the most simple alkane, methane.  This means that the compound contains 1 carbon atom and 4 hydrogen atoms.  The trend for the other compounds is increasing the number of carbon atoms.  Since the first one is methane with 1 carbon and 4 hydrogen, the next compound would be ethane which contains 2 carbon and 6 hydrogen.  As you gain more carbons, the number of hydrogen is 2 more. 
Here is a table of the simple alkanes:

# Carbon

Name

Molecular Formula

Structural Formula

1

Methane

CH4

CH4

2

Ethane

C2H6

CH3CH3

3

Propane

C3H8

CH3CH2CH3

4

Butane

C4H10

CH3CH2CH2CH3

5

Pentane

C5H12

CH3CH2CH2CH2CH3

6

Hexane

C6H14

CH3(CH2)4CH3

7

Heptane

C7H16

CH3(CH2)5CH3

8

Octane

C8H18

CH3(CH2)6CH3

9

Nonane

C9H20

CH3(CH2)7CH3

10

Decane

C10H22

CH3(CH2)8CH3

Here is a video:

Bohr Model

The image above is the picture of the bohr model for Cl.  The bohr model shows the electron levels of the element that you want to draw.  Just find out how many electrons are in the element and then fill in the number of electrons in the proper shell.  There are limits for each shell.  They follow as:
1st shell : 2 electrons max
2nd shell : 8 electrons max
3rd shell and all others : 8 max

For example carbon has 6 protons and since we are drawing a carbon atom without a charge it has a overall charge of 0.  This means that there are 6 electrons.  The bohr diagram will look like:

Here is a video:

Lewis Diagrams

What is that picture? That is the lewis structure model of H2O, water.  This diagram shows the bonding between atoms of a molecule and the pairs of electrons that exist within the molecule.  This diagram is used to for showing covalently bonded molecules and compounds. 

To draw this, you have to follow these steps:
Step 1: Count up the number of valence electrons for each atom, and total them up to give the total number of electrons for the molecule

Step 2: Determine which atom is the central atom and join all the atoms using only single bonds. Sometimes which atom is the central atom is hard to determine

Step 3: Add lone pairs to each atom as necessary so that each atom has an octet (except H which can only have 2 electrons total) when you count all the atom's lone pairs and two electrons for each of its bonds.

Step 4: If the total you got in Step 1 is the same as in Step 3, you're done! If it doesn't you'll need to make some changes. If the number of electrons in Step 3 is larger than in Step 1, you must add double bonds as necessary between atoms. Then adjust the number of lone pairs again so that each atom has an octet. **Remember no double bonds to H or with any of the halogens!** If the total electron count with only single bonds is smaller than in Step 1, you probably made a mistake somewhere. Go back and double check.

Step 5: Continue adjusting the arrangement of single and double bonds and lone pairs (and also triple bonds if necessary) until the total electron count matches what you got in Step 1.

Here is a video: