Electron Dot and Lewis Diagrams

So electron dot and lewis diagrams are just one way of modelling an atom/element. However, in these diagrams, it only requires the valence electrons. Today we are going to learn how to draw them and it's actually very simple. *Sorry if the pictures don't show up!! Don't know why it keeps doing that...*

Before we start though, here's some general information you should know about the diagrams:
- The atomic symbol represents the nucleus. Therefore you should write it in the middle.
- You must know the amount of valence electrons to draw the diagram
- Dots around the symbol represent the electrons
- There are four orbitals (one on each side of the nucleus) and each one can hold a maximum of 2 electrons
- Each orbital must have 1 electron before they start pairing up
- All valence electrons must be used
- Each element must have a full valence shell (8 electrons) except for H (2 electrons)

Ok now let's start making diagrams!
Ex. CH4
Step 1: Find the central atom. It's the one furthest from a full shell.
C=4 and H=1 but since H only needs 2 and C needs 8 then C is furthest away from a full shell therefore it is the central atom.

Step 2: Put C in the center to represent the nucleus then draw the dots around it to represent the valence electrons. Once you've done that, draw the H's around the C to make sure that they all have a full shell.

 And VOILA! YOU'RE DONE :D

If you want to do a structural diagram, just replace 2 electrons with lines. So it would look something like this..

Well that covers the basics of it. Here's a video about more complex dot diagrams such as ionic and covalent compounds. 

http://www.youtube.com/watch?v=QKoA3fZ29B0&NR=1

FUNctional GROUPS! how FUN. (:

what is a FUNctional group??
well....
here;s the definition.
Functional groups: is a specific group of atoms in a molecule and gives the molecule the ability to respond in a specific manner.

hmm?
(:

they are :

• organic compounds that have carbon and hydrogen.
• can be a single or a group
• the most popular ones are:

floro (F), Chloro (Cl), Bromo (Br), Iodo ( I)

and finally nitro (NO2)


Properties of Halogens:

• insoluble in water
• unreactive hydrocarbon such as the Teflon
• anything with Cl or Br are more reactive than others
• anything with I on the other hand is even MORE reactive

Properties of Nitro:

• insoluble in water 
• unreactive to chemical attack
• explosive
• have a nice smell or odor

ALCHOLS

• are organic compounds that contains OH

• they can be name by finding the longest chain and replacing the e.
• soluble in water
• poisonous

Note: alcohol chain has the lowest possible chain   

********NEED TO KNOW*********

ALDEHYDE:

- organic compound THAT HAS C=O group at the end of the hydrocarbon chain
- it follows the standard rules
-changes the parent chain ending to "al"
-soluble in water and reactive

MULTIPLE-OH

- a compound has MORE THAN one -OH group number 
-add a -diol, -triol etc ... in the ending 

Ketones

-organic compound that has C=O group at end of the hydrocarbon chain
- it follows the standard rules  and add "one" at the ending to the parent chain

• soluble in water but unreactive

 

VIDEO TIME!!!!!!!!!!

 

did you guys have fun watching those videos?
oh just say yes.
"yes"<- anonymous person.
"yay!!" <- me

yes. im crazy.
O.O


bye everyone!!
have FUN studying!

Alkenes and Alkynes

Alkenes 
to start off, let's look at a visual!

( here's chemical structure of an ethylene)

                                                                                   A.K.A. ( also know as)

 moving on..

• hydrocarbons with double bonds make up this family ( alkene )
• it's unsaturated
• they are also insoluble and flammable
• and the ending changes from ane to ene 

**The formula for alkenes is C_nH_2n**

Rules for naming


Step 1: fine the longest chain
Step 2:  find the # of carbon to get the lowest # for the start of the double bond; then place that number   before the name 
Step 3: name and number all the side groups and arrange them alphabethically.

FOR EXAMPLE: 

CH3CH=CHCH3

- so, the longest chain is.. four. so that's butane 

- now remember to change the ending into ene

- now the bond is located at the second place

- so you call this.. 2-butane.

(pretty easy ryt?)

how about this one?

give it a try.  

     CH3     CH3
      |       |
CH3CH2CHCH2CH=CCH3

 since the double bond is at the end. you count starting from RIGHT to LEFT.

answer: 

2,5-dimethyl-2-heptene

 Alkanes with two double bonds are called dienes, those with three are called trienes, and so on...

Now, when it comes to alkenes, some molecules will have the same structure but they have different geometry.

 "Cis" and "Trans"

geometric isomerism among alkenes.

• this is used so we can differentiate 2 chemical formulas that are the same but are arranged differently.
• "cis" and "trans" are the two geometric isomers
• "cis" means on the same side
• "trans" means on the opposite ends

FOR EXAMPLE:

cis-2-butene

CH3     CH3  ( see how CH3 are on the same sides ?)
 \     /
  C = C
 /     \
H       H

trans-2-butene

CH3     H   ( see how CH3 are on the opposite sides?)
 \     /
  C = C
 /     \
H       CH3

here;s a better visual picture (:

LEFT PICTURE: cis-2-butene

RIGHT PICTURE: trans-2-butene 

**Note: that if the top and bottom are the same; there's no need to use cis or trans.**

Alkynes 

• now alkynes have the same rules as alkenes except they ends with yne 

  • compounds with low polarity

    • have one or triple bond

      • formula is  CnH2n-2

        for example:

        

  Here's a diagram for more examples of different types of alkyne and alkene's molecular formulas.

  

   still dont get it?

  here's some videos you can watch.

   
  
  
  
  

sry fellow bloggers but i have no joke for today. 

i dont feel like being funny today.

so good day to u all!

or should i say goodnyt!

ta-ta

O.O 

Organic Chemistry Part 1

Organic chemistry is defined as the chemistry of CARBON compounds.  
Carbon can produce millions of molecules is related to its electron structure.  Each carbon has four electrons available for bonding which can be shared in four covalent bonds with other atoms.
They can lin with other atoms in single bonds/double/triple bonds

Alkanes 

• are a hydrocarbon in single bonds
• non polar molecules
•  saturated: not possible for another atom to bond to the structure
• end in ane
• formula: CnH2n+2

• can have side branched called substituted hydrocarbons
• alkyl group: an alkane which has lost 1 hydrogen can be attached to them

• alkyl goup cannot esist by themselves, they must be attached to a larger hydrocarbon

• the longest chain of carbon determines the parent name of the hydrocarbon

• carbons in the parent are numbered consecutively so that groups are indicated by the lowest numbers

• the position of each attached group is indicated by a number

• if there aremorethan 1 type of alkyl goup, list them alphabetically,  put its position number in fount, put a dash between each alkayl

a nice online teacher....

nice video to watch

Chemical bonding

1. The electrostatic forces between charged particles    
first of all.... you have to know this two terms.

bond energy - the energy involved in the processes of bond forming and bond breaking, a measure of bond strength
electrostatic force - a force existing as a result of the attraction or repulsion between two charged particles.

• opposite charges attract each other  (eg. proton and proton)

• same charges repel each other (eg. proton and electron)

when attractive force is greater than repulsive force, a chemical bond is formed.  This is a situation in which a pair of electrons is simultaneously attracted to two atomic nuclei.  two oppositely charged particles approach each other, the potential energy decrease.   For many atoms, the formation of a chemical bond with another atoms leads to a decrease in the energy of the system.

When an atom is involved in a chemical bond, some of the atoms' orbitals are modified to allow electrons to be shared between two adjacent atoms. However,  atoms share electrons but not necessarily equally....this leads to the next topic

2. types of chemical bonding
In science 10, we learned that chemical bond can be either ionic or covalent and now in chem 11, covalent bonding can be divided into two new categories:  polar or non polar. This classification is based on whether the electrons are shared equally.
Here are the three types of bonding:

1. ionic bond - the electrons are transferred from metal to non metal.  
2. non polar bond- the electrons are shared equally
3. polar bond - the electrons are not shared equally

To find out which type of bond is formed, you have to know their electronegativity.
Electronegativity of an atom is the tendency of the atom to attract electrons from a neighbouring atom.
In general, values increase from left to right and decrease down a group
Most is flourine and least is celsium

when the difference of two atoms is:
less than 5... a covalent bond is formed
between 0.5 and 1.8....a polar covalent bond is formed
greater than 1.8... an ionic bond is formed

3.a closer look to polar covalent compounds
Polar covalent bonding
the atom with the great electronegativity will pull the electrons in the onds, move time will spend on this electron
the atoms:
with higher electronegativity will form a partial negative charge
with lower electronegativity will form a partial positive charge

here is a more detailed video about polar covalent compounds

Bohr Models

So, who is Bohr and why is he important you ask?
Well, its this guy right here..

Anyways, he contributed a lot to chemistry and our understanding of atoms. One of them is creating the Bohr model, which is a diagram of the atom showing that electrons orbit around the nucleus in the center. 

When electrons absorb energy, they are capable of jumping up to a higher orbital/shell.

But when electrons move from a higher shell to a lower one, they release energy as a photon of light, which is then emitted from the atom. 

The strength of the energy causes an atom to have different colours from each other or in other words, they create their own spectra of light.

Now it's time to learn how to draw your very own Bohr model, yay!

1. Figure out how many protons and neutrons there are in the element. As an example we'll use Sodium. To find out how many protons there are, look at your periodic table and find Sodium. Then look at the atomic number and you've found the protons! Now for the neutrons, you just have to subtract the amount of protons from the atomic mass and voila! (Round up to the nearest whole number)

2. Now that you've found the number of neutrons and protons, write it in the middle to represent the nucleus. Instead of writing the full word out though, just write "p" as proton and "n" as neutron.

3. Then you find the number of electrons. In this case it's 11. Now that we know that, we can draw the orbitals around the nucleus. Each shell has a maximum amount of electrons it can hold. The first one (closest to the nucleus) can hold a maximum of 2. The second a maximum of 8. The third one can hold a maximum of 8-18 and so on. Also, when drawing the electrons, they should form 4 groups of 2 around the nucleus. So it should look a little something like this: 

Thanks for reading. I hope you understand everything >.> and if you don't, then for further (probably better) explanation, watch this video :)

http://www.youtube.com/watch?v=iih6rJ2S6pk

Trends on the Periodic Table

There are many different trends on the periodic table. Here is a list of the different trends:

1. Metallic Properties
2. Atomic Radius
3. Ionization Energy
4. Electronegativity
5. Reactivity 
6. Ion charge
7. Melting/Pointing Point
8. Density

Metallic Properties

- Metallic to non metallic = left to right

- Elements = more metallic going down a family in the periodic table

Atomic Radius

- Decreases going across a row left to right

- Increases going down a group

- Going left to right = atomic number, protons, and positive charge increases

- Increases in the number of electrons surrounding the nucleus

- All electrons have same average distance from the nucleus

- More protons = less distance between the electrons and the nucleus

General Trend

- Atomic size decreases left to right

- Increases down a column

Reactivity

- Most reactive metal = Francium

- Most reactive non metal = Fluorine

Ion Charge

- Depends on their group/column

Melting Point/Boiling Point

- Highest = The centre of the table

- Noble gases =  Lowest

- Left to right = increase (until the middle of the table)

Ionization Energy

- Needed to completely remove electrons from atoms

- Increases going up and to the right

- Noble gases have high ionization energy

- Helium has the highest IE

- Decreases going down

Electronegativity

- How much an atom wants to gain electrons

- Same trend as Ionization Energy

- High electronegativity attracts neighbouring atoms' electrons and might remove them completely

- High electronegativity = high ionization energy

- Fluorine is the most electronegative element

History of the Periodic Table

Here's a little bit of information on how the wonderfully organized periodic table was invented. Yes, it's true; the periodic table didn't always exist :p So, first of all, we needed know some elements before we could even organize them. By 1917 we had already discovered 52 elements and it was rapidly increasing. By 1863 a total of 62 elements were discovered. The first few attempts to organize them was in the 1920s but nothing really got done.

- In 1857, Willy Odling seperated the elements into 13 different groups based on their physical and chemical properties. It had its flaws but it was a good start.

- Between 1863 and 1866 a guy named John Newlands discovered that by ordering all the known elements by their masses, every eighth element had something in common. This became known as the Law of Octaves. However, this method did not allow him to predict new elements.

BREAKTHROUGH!! YAY :)

 (Nice hair hehe)

- In 1869 Dimitri Mendeleev organized the elements according to their mass and properties. When he did this, he realized he was on to something...and indeed he was. :p
- When he listed them according to their mass, he noticed that certain properties recur periodically. (Oooh so that's why it's called the periodic table)
- He then broke the list into rows (period) and columns (group)
*So in other words, Dimitri was the first to make a periodic table
- He was able to predict the properties and characteristics of undiscovered elements very accurately
- This allowed chemists to organize and understand their data + predict new properties (which is very useful!!)

Modern Periodic Table
- The periodic table we use today is organized according to atomic numbers. (Incase you didn't notice..)
- Periodic Law: Properties of the chemical elements recur periodically when the elements are arranged from lowest to highest atomic numbers.

Major Divisions in the Periodic Table
Period: The set of all elements in a given row going across the table.
Group/Family: The set of all elements in a given column going down the table.


Chemical Families
Now that we know a little more about the history of the periodic table, lets learn about the different groups and families that can be found on the table. As you can see in the above picture there are many different types of elements and each one is separated into their own little groups. Here's a little bit more information on the different families.

*In case you didn't look at the above picture...
Alkali Metal: Elements in the 1st column (except hydrogen).
Alkaline Earth Metals: Elements in the 2nd column.
Halogens: 2nd column from the end on the right hand side. Starting with fluorine.
Noble Gases: Far right side of the table starting with helium.
Lanthanides: Elements in the 1st row shown under the table, starting with lanthanum.
Actinides: Underneath the lanthanides, starting with actinium.


Metals
- Reflect light when polished.
- Shiny and metallic lustre.
- Opaque
- Good conductors of electricity and heat
- Flexible when in sheets
- Malleable (Hammered or rolled into sheets)
- Ductile (Drawn into wires)
- Solid at room temperature (Except mercury)
- Lose electrons


Non-Metals
- Gas, liquid, brittle solid at room temperature
- Poor conductor of heat and electricity
- Solids = dull to lustrous and opaque to translucent 
- 2 types of non metals:

• Very low electrical conductive 
• Fair to moderate conductivities

Semiconductor

- Non metal with electrical conductivity, it increases with higher temperature

- Metalloids/Semimetals have properties that look more like metals than non metals

- Metal conductivity decreases with increased temperature 

- Metalloid's conductivity increases with temperature

Electron Configuration (Orbitals, Valance Electrons, and Core Notation)

The electron configuration of an atom is a form of notation which shows how the electrons are distributed among the various atomic orbital and energy levels.  

before we start, you have to know these principles so you can fill the electrons correctly.
 

I.  Principle Quantum Number (n) and Sublevels

The number of sublevels that an energy level can contain is equal to the principle quantum number of that level.  So, for example, the second energy level would have two sublevels, and the third energy level would have three sublevels.  The first sublevel is called an s sublevel.  The second sublevel is called a p sublevel.  The third sublevel is called a d sublevel and the fourth sublevel is called an f sublevel.  Although energy levels that are higher than 4 would contain additional sublevels, these sublevels have not been named because no known atom in its ground state would have electrons that occupy them.

II.  Sublevels and Orbitals

An orbital is a space that can be occupied by up to two electrons.  Each type of sublevel holds a different number or orbitals, and therefore, a different number of electrons.  s sublevels have one orbital, which can hold up to two electrons.  p sublevels have three orbitals, each of which can hold 2 electrons, for a total of 6.  d sublevels have 5 orbitals, for a possible total of 10 electrons.  f sublevels, with 7 orbitals, can hold up to 14 electrons.  The information about the sublevels is summarized in the table below:

Table 3-6a - Orbital and Electron Capacity for the Four Named Sublevels
Sublevel	# of orbitals	Maximum number of electrons
s	1	2
p	3	6
d	5	10
f	7	14

III.  Total Number of Electrons per Energy Level

An easy way to calculate the total number of electrons that can be held by a given energy level is to use the formula 2n².   For example, the fourth energy level (n=4) can hold 2(4)² = 32 electrons.  This makes sense because the fourth energy level would have four sublevels, one of each of the named types.  The s sublevel hold 2 electrons, the p sublevel holds 6 electrons , the d sublevel holds 10 electrons and the f sublevel holds 14 electrons.  2 + 6 + 10 + 14 = 32, so the formula 2n² works!  We can summarize this information in the table below:

Table 3-6b Orbitals and Electron Capacity of the First Four Principle Energy Levels
Principle energy level (n)	Type of sublevel	Number of orbitals per type	Number of orbitals per level(n2)	Maximum number of electrons (2n2)
1	s	1	1	2
2	s	1	4	8
	p	3
3	s	1	9	18
	p	3
	d	5
4	s	1	16	32
	p	3
	d	5
	f	7

  

V.  Order of Filling Sublevels with Electrons

The next thing that you need to recall is the fact that the energy sublevels are filled in a specific order that is shown by the arrow diagram seen below:

Remember to start at the beginning of each arrow, and then follow it all of the way to the end, filling in the sublevels that it passes through.  In other words, the order for filling in the sublevels becomes; 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d,7p.

So, how to find the numbers of valance electrons?

Its easy!  you just need to add all the electrons in s and p sublevel

Then, how do you write it in core notation.

First, you have to find the noble gas at the front role

Then, you add electrons until you get the number of electrons you want

eg. C = [He]2s²2p²

Isotopes and Molar mass

Before we start the lesson, its good for us to play this game.  It can help us to get a basic idea of isotopes and atomic mass

http://phet.colorado.edu/zh_TW/simulation/isotopes-and-atomic-mass

So, Isotopes are atoms which have the same atomic number but different mass numbers.   In Other words, they have the same number of protons but different numbers of neutrons.

The number of neutrons in an atom can vary within small limits.
Eg. there are three kinds of carbon atom ¹²C, ¹³C and ¹⁴C. They all have the same number of protons, but the number of neutrons varies.

	protons	neutrons	mass number
carbon-12	6	6	12
carbon-13	6	7	13
carbon-14	6	8	14

These different atoms of carbon are called isotopes.

Molar mass of a substance combined by isotopes
Eg.
Carbon can be formed by these isotopes.
90.% of carbon-12, 5.0% of carbon 13 and 5.0 % of carbon 14

We can calculate this particular substance's atomic mass by:
  12x0.90 + 13x  0.050 +14x0.050
=   12.15  (2 sig fig)
=   12g