Monday, November 9th, 2009

Today we saw the topic “Chemical Balancing". Chemical Balancing is a way to balance an equation, and there are 3 methods but today we saw the Trial and error method also known as Inspection method.

We can ask first of all why we need to do it, well we need to follow the rule “matter can’t be created nor destroyed just transformed”.

To make a chemical balance first you need an equation:

Na + Cl → NaCl (It’s not balanced)

Then you need to write the amount of molecules of each element:

Na + Cl2 → NaCl

Na 1 Na 1

Cl 2 Cl 1

If you notice, the amount of Chlorine is not the same and we need to apply the rule of “matter can’t be created nor destroyed just transformed”. So we need to aggregate numbers to balance the equation:

Na + Cl2 → 2NaCl

Na 1 Na 2

Cl 2 Cl 2

Now we balanced Chlorine but now Sodium is not balanced, so we need to aggregate another number:

2Na + Cl2 → 2NaCl

Na 2 Na 2

Cl 2 Cl 2

Now the equation is balanced with the same amount of molecules before and after the arrow.

Michelle Torrero

Friday, November 6th, 2009

Today the class started with awful news: The test is on November 20^th!

So if anyone else was planning to go to the New Moon´s premier you need to come early to school, even if you´re sleepless.

So...

Today´s theme was Chemical formulas and equations

An equation can tell you the elements that you have, the cuantity and, in some cases, the state or compatibility.

A chemical formula is a concize way of expresiing information about the atom that constitute a particular chemical compound.

Every compund that exists has an specific formula.

There are some elements that don´t come alone. They come in pairs:

H2

O2

N2

F2

CL2

BR2

I2

There was another theme today: Types of chemical reactions.

All chemical reactions involve a change in substances and a change in energy. Neither matter or energy is created or destroyed in a chemical reaction, only changed.

There are four types:

SYNTHESIS REACTION
In a synthesis reaction two or more simple substances combine to form a more complex substance.

DECOMPOSITION REACTION
In a decomposition reaction a more complex substance breaks down into simpler parts. Synthesis and decomposition reactions are opposites.

SINGLE REPLACEMENT REACTION
In a single replacement reaction a single uncombined element replaces another in a compound.

DOUBLE REPLACEMENT REACTION
In a double replacement reaction parts of two compounds switch places to form two new compounds.

Erin Alice Gil

The homework was:

Find 3 examples of each type of reaction.

Friday October 30th 2009

On Friday's class we learned about Covalent Bonds.
A Covalent Bond its when atoms share a pair of electrons. The difference between this one and a Ionic Bond its that an ionic bond needs to lose or gain electrons and become positive or negative and covalent bonds just share (both have and use the electrons if they need it).
For example: H= that has 1 valence electron and needs just one to be stable -----> Both can form H2O by a covalent bond.
O= which has 6 valence electrons and needs 2 to be stable
A characteristic of covalent bonds its that are "Polar Molecules", that means that the atoms has more positive charge in one side and negative charge in the other. We can use water (H2O) as an example in this too.




It has positive charge in the Hydrogen side and and negative charge in tho Oxygen side because of the excess of electrons.
(the red one is Oxygen and the whites are Hydrogen.)















When all the class understood this we made an activity outside, we made a covalent and a ionic bond simulating to be atoms (neutrons, protons and electrons).

Laura Carrillo

Monday October 26th 2009

Today we talked about ionic bonds, but class started with a review of what makes up an atom. Which is the proton (positive), electron (negative), and neutron (neutral). Then he went on to tell us that each atom has the same number of neutrons, protons, and electrons, but that the mass is different; For this one is in a way the sum of the neutrons and protons (it is also the electrons but they barely make a difference so it is not very noticeable). Then we got to the actual subject IONIC BONDS.
To know what that is we need to understand what ions are: The elements that have charges, there are two types: Cations (positive) and Anions (negative).
Now to get there we need to discuss metals and nonmetals.
"Atoms of metals tend to lose their electron valances leaving a complete octect in the next energy level."
Which basically tells you that metals tend to give up electrons.
Example: Na (z=11) configuration= 1s²2s²2p⁶3s¹which means it has 1 valance electron, and in order to be like a noble gas it has to lose one electron by doing this the atom goes from neutral to positive because now it has more protons than electrons. So it becomes a cation of sodium, because when they become cations they don't change the name.
-When you look at the periodic table: the number in the top right corner with the negative and positive charge tells you how many electrons ot gives or takes away and whether it becomes a positive or negative charge.
You can also look at he columns (1a, 2a, 3a, etc.) to know how many it loses.

Once an atom becomes a cation or anion it becomes different than the original even if it's a small different it can cause a lot of changes.


"Atoms of nonmetals tend to gain electrons or to share electrons with another nonmetal to achive an octet."

(most not all)

example:Cl (z=17) configuration= 1s²2s²2p⁶3s²3p⁵so it needs one more electron to become a noble gas, and by gaining an electron it emds up having more electrons than protonsand is negative instead of neutral. There are some that become pseudo noble gas because they're not exactly a noble gas but they are stable.
When an atom becomes an anion you change the name by replacing the last syllable with -ide.
ex: Chlorine -> Chloride.

Now the best way to know if it loses or gains electrons is by looking at it's valance number:
if it's 1-3 it loses
if it's 5-7 it gains
if it's 4 then it's a metalloid and it can do either, lose or gain.

If you've paid attention you've realized that despite me saying we were going to talk about ionic bonds I have yet to say anything about them, that's because you need to know evrything I've just said before you understand what's next.
Ionic Bond is held together by electrostatic forces.
Metal cation + Nonmetal anion = Neutral compound
(+) (-) (±)

Ex:
Na (+1) + Cl (-1) = NaCl

(P.S. Cations always go first it would never be written ClNa)

That was the whole class, and there was no homework.

Victoria Bracamontes

Friday, october 16th, 2009

CLICK TO ENLARGE

Erin Alice Gil

Monday, October 5th, 2009

Today we saw a new theme: the periodic table.

First the teacher shows us a little bit of the past:

· 1860, only 60 elements were known.

· They knew only the basic stuff.

· Jöns Jakob Berzelius- made the 2 letter system for elements.

· Johann Döbereiner- was the 1^st to “organize” the periodic table by the Law of Triads (groups of 3 elements because of their property.)

· John Newlands- use the Law of Octaves (groups of 8 elements), and he relate it with music scales.

· Mendeleev- He was the real 1^st one who made a periodic table with 12 columns and 8 rows, also we left blank spaces – he predicts the properties of the missing elements. He was considered “Chemist of predictions.”

· Henry Moseley- he organized it by atomic numbers.

As well, teacher Ariel explained us the 2 letter system for elements, that is to use the first letter of the name in English; but also why some elements are not in that system, and that’s because some elements were first written in Latin and they kept that name like gold (Au) means Aurum in Latin, and after that, he gave us a list of the 5 elements in Latin:

*Aurum (Au) = Gold

*Kabium (K) = Potassium

*Natium (Na) = Sodium

*Ferrum (Fe) = Iron

*Argentums (Ag) = Silver

· Of all the elements, 83 elements are stable in nature, while 24 are not from earth.

Now, the periodical table is conformed of rows (horizontal) and columns (Vertical):

The horizontal are the Periods-the mass and size are similar in each period.

The vertical are the Groups, and in these one are different classification:

1) Alkali Metal

2) Alkali earth metal

11) Coinage Metal- soft metals (gold, silver and copper)

17) Halogens- they separate vey easy.

18) Zero, Noble gases, Inert gases- the ones that are stable.

· Periodical table also use the electronic configuration helping you find a element more quick; the periods will be used as the biggest number of the list, example: if you got as the biggest one 3p⁴, then the period will be #3; and the groups are represented in these way:

Andrea Favela

Fridat, october 2nd, 2009

Today at the beginning Mr. Ariel said that he wasn't going to ask who found the homework hard, because apparently most of us had sent him e-mails asking for help, and he wet on to explain how it should've been done. When he drew it, one of the students realized that he had forgotten to tell us something when it comes to drawing the electrons in their shell. We thought that we were just adding the next drawing of the levels when really we were supposed to have 2 "s" levels and then the first "p" leve, when most of us thought that we only draw the s level once and then the p and so on, so he made it clcear that we're suppossed to draw the "s" level once again as we get to a new level. Also he gave us a hand out that tells us the order of the electron configuration and said that that would help us understand how to place the electrons. It looked something like this, with arrows telling you to go diagonally down from right to left:

1s
2s 2p
3s 3p
4s 4p 4d
5s 5p 5d
6s 6p 6d 6f
7s 7p 7d 7f
Also it had a picture of Bohr's model of the atom and it had how many electrons could fit in each of the levels and the order of them. And he explained it as if it was a concert stadium with all the seats beong the same price. First you fill the front row tickest which aare 1s and 2s then you move on to the ones that get farther and farther away. We did a buch of execercises with them and the first 5 to finish one of them would get an extra point in the test. One of the questions was the electron configuration of Gold (79) which was:

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d⁹

And he left Platinum's electron configuration for homework.

Victoria Bracamontes