HOLY MOLEY

Avogadro's Numbers
-atoms and molecules are extremely small and contains too many to count or weigh individually.
-Amedeo Avogadro proposed that the number of atoms 12.00000g of carbon be equal to a constant (this is equal to 1 mol of carbon)
-this value is also called Avogadro's number and forms the basis of all quantitive chemistry.


Avogadro's Number: 6,020,000,000,000,000,000,000,000 = 6.02x10 to the power of 23
-1.0 mole = 6.0x10 to the power of 23
-1 mole is simply a multiple of things.
*one mole represents a huge number of particles*
eg: 1 mole of blood cells would be more than the total number of blood cells in every human on earth.


EXAMPLE: 
- A sample of carbon contains 2.47x10 to the 25 atoms. How many moles of carbon is this?
 [ *write down what you are given]
 [ *identify what to cancel ]

**remember: your significant digits & to always put your units!

Post by the awesome Ivy Gloria

UPDATE

Here's what has happened during the last 3 classes:

We had a....

Hydrate Lab

 Discussion: Hydrates are ionic compounds that contain an inorganic salt compound loosely bound to water. The purpose of this experiment is to determine the empirical formula of a hydrate. In this lab we determined the anhydrous (without water) mass of the hydrate. We compared this with the actual mass of water that should have been present. 

..

 Materials Used: - Bunsen burner
- Test tube
- Test tube rack
- Test tube clamp
- Weight scale Procedure 1. Fill a test tube about 1 cm with the hydrate
2. Carefully place the test tube on the scale and record the mass of the hydrate and test tube
3.
4. Pick up the test tube with the clamps and carefully hold it in above the Bunsen burner
5. Gently heat the test tube by moving the test tube in and out of the flame for about 5 minutes or until all the water has boiled away
6. Carefully re-weigh the test tube ensuring none of the chemicals inside spill Using extreme caution, connect and light your Bunsen burner. Adjust the gas flow until the flame is about 5 cm tall

...
The following class after the Hydrate Lab, we had a test for Unit 2: The Atomic Theory

During today's class (November 12th, 2010), we had special guests (Japanese students) that visited us from Japan. We had very little time to do anything, however, so we went over our test which was fairly o.k.

-Ren Flores

Naming Compounds

Today we learned about Chemical Nomenclature (giving something a name)

Up to this date, the most common system is the IUPAC (International Union of Pure and Applied Chemistry) and this is a system of naming Chemical Compounds such as

• Ions
• Binary Ionic
• Polyatomic Ions
• Molecular Compounds
• Hydrates
• Acids/Bases

Chemical Formulas:
Be aware of the differences between an ION and a Compound!

What is the difference between an Ion and an atom?

An Ion makes up the electric charge of an atom. It can be a positively (+) charged atom or a negatively (-) charged atom, depending on the number of protons versus electrons.

On the other hand, an atom is the smallest part of an element composed of electrons, protons, and the nucleus.

To add onto Multivalent Ions, some elements can form more than 1 ion. The most common ion charge is listed first, on the top right hand corner. Example: Iron has 2 charges +3 and +2, so +3 would be the more common charge and we use it when it is not given to us.

Multivalent Ions:

Classical systems uses latin names of elements and the suffixes (Listed Below)

For example, to represent Iron and Oxide, we would say Ferric Oxide. Note that ending of Ferr, which is the latin name for Iron is -IC, so we know that the charge used is the top one which is the more common/larger charge.

Another example: Plumbic Oxide, which would be Pb2O4 which simplifies to PbO2

Mercuric Fluorode -> HgF2

COMPLEX IONS

-Complex Ions are large groups of atoms that stay together during a Chemical reaction
-Almost all are anions (Most polyatomic ion has a negative charge with Ammonium being an exception since it has a positive charge)
Examples: Sulphate, Cyanide, Nitrate are all Complex ions

What is the chemical formula for sodium nitrate?
----------   NaNo3
Ferrous Sulfite? Fe (+2)So3(+2) --> FeSo3
--------------------------------------------------------------

We also learned about HYDRATES:
-Some Compounds can form lattices that bond to water molecules such as:
  a) Copper Sulfate
  b) Sodium Sulfate
-These crystals contain water inside them which can be released by heating!

To name Hydrates:
1.Write the name of the Chemical formula
2.Add a pre-fix indicating the number of water molecules (mono=1,do=2,tri=3,tetra=4,penta=5,hexa=6,etc)
3.Add hydrate after the prefix

ie. Cu(SO4) • 5 H20 -> Cuppric Sulphate or Copper (II) Sulphate
     Li(ClO4) • 3H2O -> Lithium Perchlorate Trihydrate

Note: Even if there is only one atom present of the second non-metal in the compound, always use the prefix “mono”. Here are the pre-fixes used:

• One —-> Mono
• Two —-> Di
• Three —-> Tri
• Four —-> Tetra
• Five —-> Penta
• Six —-> Hexa
• Seven —-> Hepta
• Eight —-> Octa
• Nine —-> Nona
• Ten —-> Deca

Lastly, we learned how to name ACIDS and BASES

-HYDROGEN compounds are ACIDS
-Hydrogen appears first in the formula unless it is part of a polyatomic group such as
CH3COOH---> Polyatomic Acid = Acetic Acid

ie. H2SO4 --> Sulfuric Acid

Hydroxide, or OH- is found in Bases.
-name as binary ionic

ie. NaOH ---> Sodium Hydroxide
Ba(OH)2 ---> Barium Hydroxide

...and there you have it!

-Post by Ren Flores Aka Birthday Boy who posted a Chem post on his birthday.

  

QUANTUM MECHANICS:

The basis of quantum mechanics came from Neils Bohr’s theory in 1920...

BOHR THEORY
- the electron is a particle that must be in orbital in the atom

QUANTUM THEORY
- the electron is like a cloud of negative energy or a wave
- the electron wave stays in certain orbitals
- orbitals are areas in 3D space where the electrons most probably are (*Note: we can never be 100% sure the electron is exactly in a certain place, since it is said to be a wave of energy)
- the energy of the electron is in its vibrational modes (like notes on a guitar string)
- photons are produced when high energy modes change to lower energy modes (Example: energy from the electron is released as light, aka a photon)

The orbitals contain electrons moving around in that area. The orbitals may overlap eachother; the differences between the orbitals (as we know so far) is that they can be larger spaces, smaller spaces, or situated in different sides.
(*Note: ignore the numbers and words on the pictures. The pictures are just examples of where the orbitals may be situated in the atom.)

S Orbitals
- there is 1 suborbital
- each orbital holds 2 electrons
- total electrons: 2

P Orbitals
- there are 3 suborbitals
- each containing 2 electrons
- total electrons: 6

D Orbitals
- there are 5 suborbitals
- each contains 2 electrons
- total electrons: 10

F Orbitals
- there are 7 suborbitals
- each contains 2 electrons
- total electrons: 14

How the orbitals correspond to the periodic table and elements:

*Note: if an element is under, let's say "2p", it has all the other orbitals filled too, so that would be 1s, 2s, 2p. Geddit?

For Bohr models, we know we draw engery levels and little dots for electrons.
For Lewis Diagrams, we graw the outer shell with dots for electrons.
So how do we express a certain element with it's electrons using this Quantum Mechanic theory?

Example:

Fluorine
1) Find the element on the periodic table

2) Figure out how many orbitals its electrons take up (you can use the previous chart to figure this out, just match the positions!)

So, it's in the 2p section, which means its electrons take up the orbitals 1s, 2s, 2p

3) Next, find out how many electrons it has and figure out how many are in each orbital

Fluorine has 9 electrons

(Since each S orbital can hold 2 electrons...)

1s holds a max. of 2 electrons

2s holds a max. of 2 electrons

(Since each P orbital can hold 6 electrons...)

2p holds a max. of 6 electrons

So Fluorine would look like:

1s(2) 2s(2) 2p(5)

(*bracket numbers = the number of electrons in each orbitals)

And you're done!

Try it out using Sodium

Highlight for answer: 1) 1s(2)2s(2)2p(6)

BOHR DIAGRAMS

Bohr Diagrams:


-Atoms are electrically neutral (the number of protons equals the number of electrons)


- Two different models can be used to describe electron configuration
         -Energy Level Model
         -Bohr Model


- electrons occupy shells which are divided into orbitals


The Bohr diagrams places the number of neutrons and protons in the center and electrons in energy rings around the outside. Each energy ring has a maximum number it can hold

Learned in class:
                     Ring 1 – 2 electrons
                     Ring 2 – 8 electrons (octet)
                     Ring 3 – 8 electrons (octet)
                     Ring 4 – 18 electrons
----------------------------------------------------------
                     Ring 5 – 18 electrons
                     Ring 6 – 32 electrons
                     Ring 7 – 32 electrons

The electrons in the outer most energy ring are called valence electrons. These electrons are very important because they are involved in chemical reactions. They can be lost or gained so that the element will have 8 electrons in the outer most ring and become stable. The noble gases already have 8 electrons in their outer ring so they are stable and do not react readily

Now its your turn to try!

Atom Structure:
http://www.youtube.com/watch?v=hpKhjKrBn9s&annotation_id=annotation_736168&feature=iv

Bohr Diagrams:
http://www.youtube.com/watch?v=hpKhjKrBn9s&annotation_id=annotation_736168&feature=iv

Here are some videos on youtube that deal with the Atomic Structure and give a detailed explanation on Bohr Diagrams. Enjoy!

-Post by Ivy Gloria. Picture by Ren Flores

ELECTRONIC STRUCTURE: DRAWING ELECTRON DOT DIAGRAMS: November 1st, 2010

Drawing electron dot diagrams:

• The nucleus is represented by the atomic symbol
• For individual elements determine the number of valence electrons (electrons in the outermost energy level of an atom; for most atoms, it is available to be gained, lost, or shared in the formation of chemical bonds)
• Electrons are represented by dots around the symbol
• Four orbitals (one of each side of the nucleus) each holding a max of 2 electrons
• Each orbital gets 1 electron before they pair up to make a lone pair (a pair of electrons- 2 of them)

An atom of Neon can be represented by the diagram on the left. But in this case, we are drawing electronic dot diagrams. For neon, we must determine a) number of valence electrions b) place dots around the element to represent the valence electrons. Since there are 10 electrons, 2 go in the first shell but the rest (8 electrons) are in the second shell, therefore, these electrons are considered to be in the valence shell, and we label them.

Lewis Diagrams for compounds and Ions:

-In covalent compounds electrons are shared

1. Determine the number of valence electrons for each atom in the molecule

2. Place atoms so that valence electrons are shared to fill each orbital.

Compound:

We have just learned how to draw a Lewis dot diagram for a single element and a compound. An Ionic Compound presented as an electronic dot diagram has the follow:

-An ionic compounds electrons transfer from one element to another

-Determine the number of valence electrons on the cation (+) and move these to the anion (-).

-Draw [ ] around the metal and non-metal (write the charges on the outside bracket)



An example of an ionic compound: Lewis Dot Diagram



 Next we have a more complicated diagram, because it consists of a "DOUBLE BOND".

DOUBLE & TRIPLE BONDS:

Sometimes the only way covalent compounds can fill all their valence levels is if they share more than one electron.

This periodic table can also help you when drawing Electronic Dot Diagrams. Notice a trend in each group (group 1 has 1 valence electron, group 15 has 5 valence electrons and so on)

Yay, you've mastered the art of drawing Electronic dot Diagrams!

Post by Ren Flores