Happy Martin Luther King Jr. Day - Be the Diamond

Our bodies are constantly replacing the cells and molecules they are composed of.

 A Carbon atom that has passed through:

Jesus, Mohammad, Moses, the succession of Dali Lamas, George Washington, Martin Luther 

King Jr., Hitler, Osama bin Laden, Kim Jong-il, and Kim Jong-un

Will pass through you at some point in your life.

I hope it changes you for the better. Happy Martin Luther King Jr. Day

Back to Basics: Atomic Structure

1

The identity of an element is determined by the number of protons in its nucleus. 

The nucleus contains positively charged atomic mass units called protons, and neutral atomic mass units called neutrons. 

So Hydrogen, for example, has one proton. All elements with one proton are Hydrogen atoms.

The mass number of an atom is the number of protons plus the number of neutrons.

Two atoms with the same number of protons, (thus the same identity) but have a different number of neutrons are called isotopes.

2

An example of an isotope would be Tritium, which is a Hydrogen atom (1 proton) with 2 neutrons.The superscript 3 in the image above is the sum of the protons and neutrons in Tritium. The subscript is the number of protons.

Protium is the most common isotope of Hydrogen, it has one proton and one electron only, no neutrons.

Another common example would be carbon- 12 and carbon-14. Carbon-12 has 6 protons and 6 neutrons, while carbon-14 contains 6 protons and 8 neutrons. There are many other isotopes of Carbon, and their molar masses average out to 12.01g per mole which is the value on the periodic table.

The molar mass we see on a periodic table is the average mass of all the isotopes of an element.

Sources:
1) "Blausen 0342 ElectronEnergyLevels" by BruceBlaus - Own work. Licensed under CC BY 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Blausen_0342_ElectronEnergyLevels.png#mediaviewer/File:Blausen_0342_ElectronEnergyLevels.png

2) "Protium deuterium tritium" by Lamiot for french version, from Dirk Hünniger - self, translation from Dirk Hünniger (german wikipedia). Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Protium_deuterium_tritium.jpg#mediaviewer/File:Protium_deuterium_tritium.jpg


3) Tro, Nivaldo J., Robert S. Boikess, Joseph H. Bularzik, and William M. Cleaver. "Liquids, Solids, and Intermolecular Forces." Chemistry A Molecular Approach. Upper Saddle River: Prentice Hall, 2008. 76. Print.

Online Chemistry Notes: Electronegativity and Polarity

Electronegativity is a word we use to describe how much an atom is pulling electrons.

The Textbook Definition is:
"Electronegativity: The ability of an atom to attract electrons to itself in a covalent bond."

Fluorine is the most electronegative element.

On a periodic table, Electronegativity increases from left to right across a row, and it also increases up a group from bottom to top.

This is an important concept in chemistry. Electronegativity reappears throughout both semesters of General Chemistry and follows you into Organic and Biological Chemistry if you take those courses. (and you should, or at least sit in on a few classes if you don't want to risk your GPA) 

It's important to understand Electronegativity because it allows us to determine if a molecule is polar. 

What does polar mean? think of it as a molecule with a positive side (pole) and a negative side (pole). Just like a magnet.

Molecules are composed of different atoms, and the more electronegative atom in a molecule will be the negative pole.

 It's pulling those electrons in the covalent bond toward itself. And electrons are negative, so the atom becomes partially negative.

 Similarly, the less electronegative atom will be the positive pole since the electrons are moving away from it.

There are exceptions to this rule. If the pulling force from the electrons, known as the dipole moment, cancels each other out due to symmetric molecular geomoetry, then there will be no net dipole moment, and the molecule will be non-polar. 

Think of CO2

"Carbon dioxide 3D ball" by Jynto (talk) - Own workThis chemical image was created with Discovery Studio Visualizer.. Licensed under CC0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Carbon_dioxide_3D_ball.png#mediaviewer/File:Carbon_dioxide_3D_ball.png

We have a carbon in the middle double 

bonded to 2 Oxygen molecules. 

These oxygen molecules are more electronegative than carbon. So in the bonds between oxygen and carbon, the electrons are being pulled toward the oxygen. 

But since the bond angle is 180 degrees, their pulling force (dipole moment) cancels each other. For that reason CO2 is nonpolar.

Let's look at another molecule H2O:

"Water-3D-balls". Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Water-3D-balls.png#mediaviewer/File:Water-3D-balls.png

Now the more electronegative atom, Oxygen, is in the center, and the two Hydrogen atoms are angled away due to 2 lone pairs of electrons on the Oxygen atom (not shown in picture).

The electrons in the bonds between Oxygen and Hydrogen will be pulled toward the oxygen making oxygen partially negative. 

Since the electrons are moving away from the Hydrogen atoms, the Hydrogen atoms become partially positive. 

Most importantly, since the molecular geometry is bent, the dipole moments do not cancel, like they do in Carbon Dioxide, and they cause a net dipole moment toward the oxygen. 

This is why Water is polar and carbon Dioxide is not.

Source:
Tro, Nivaldo J., Robert S. Boikess, Joseph H. Bularzik, and William M. Cleaver. "Liquids, Solids, and Intermolecular Forces." Chemistry A Molecular Approach. Upper Saddle River: Prentice Hall, 2008. 466. Print.

Online Chemistry Notes: Chloroform vs. Bromoform

Below are the two molecules Chloroform ( CHCl3) and Bromoform( CHBr3). They are both polar molecules, but Bromoform will have a higher boiling point because Bromine is a larger molecule than Chlorine.
                               o                                     o                         B.P = 61.7  C          B.P. = 147-151 C

 Even though Chlorine is more electronegative, and it's bonds are a little more polar, the electronegativity of Bromine is close enough to Chlorine to negate this factor. 

So since the polarity of the two molecules cancel each other out, The London-dispersion forces determine which will have a higher boiling point.For this same reason, HBr has a higher boiling point than HCl.

Here is a link from Wayne Breslyn on how to draw the Lewis Structure of Bromoform:

Source:
Tro, Nivaldo J., Robert S. Boikess, Joseph H. Bularzik, and William M. Cleaver. "Liquids, Solids, and Intermolecular Forces." Chemistry A Molecular Approach. Upper Saddle River: Prentice Hall, 2008. 466. Print.

Updated by Z. on Jan. 17, 2015

Online Chemistry Notes: Dichloromethane and polarity

The image below is a molecule called Dichloromethane.

Its'  formula is CH2Cl2. Notice the arrows? Those are dipole moments. 

Since Chlorine is more electronegative than Carbon, there are  dipole moments away from the carbon atom toward each chlorine atom. 

These two small arrows combine to make a NET DIPOLE. This is the large arrow. 

This net dipole causes the end of the molecule with the chlorine atoms to have a partial negative charge. At the same time, the Hydrogen atoms will have a partial positive charge.

 These partial (or delta) positive and negative charges cause this molecule to be polar.

Here is a Youtube video by Wayne Breslyn showing you how to draw the resonance structure: 

Do you want an A

Are you struggling to pass your chemistry class?

 Do want to go from a B to an A?

 Do you want it like this lion wants this child?

If you answered YES!, then you should use the FREE resources on this site.

Simply post your questions in the comments, and our team at CoolChemTutor.blogspot.com will start cranking out answers.

 That's how simple it is.

Online Chemistry Notes - Intermolecular Forces

(Zoom In to 200% for a better view)

Online Chemistry Notes: Questions about Quantum Numbers

1) What does the 1st quantum number represent?

The shell or energy level is represented by the principal quantum number (n). (aka the Principal quantum number

2) What is the maximum number of electrons allowed in the second shell (n=2)?

Eight. ( 2n2) is the equation for the maximum number of elections in a shell.

3) What does the azimuthal (2nd) quantum number (l) represent?

The subshell.

4) What are the first four subshells (  l = 0, 1, 2, 3)

The first four subshells are: s , p, d, f.

5) what is the formula for the maximum number of electrons allowed in a subshell?

Maximum # of electrons in a subshell = ( 4l + 2).

6) What does the magnetic (3rd) quantum number (ml) represent?

An orbital within a subshell. The possible values range from -l to l.

7) How many fourth quantum numbers (ms) are possible for an electron? What are they?

The two possible values for ms are +1/2 and -1/2.

Online Chemistry Notes: Pauli exclusion principle

The Pauli exclusion principle simply states that each electron in any atom has its own specific set of quantum numbers ( n, l, ml, ms).

Online Chemistry Notes: Heisenberg Uncertainty Principle

The Heisenberg uncertainty principle states that it is impossible to know both the momentum and position of an electron at the same time. 

The more you know about one, the less you know about the other.

This is due to the fact that the electrons change behavior if they're being observed!! Sometimes they act like a particle, and other times a wave.

Here is a great animation from

www.whatthebleep.com

Online Chemistry Notes: Isotope question

How many more protons are in a carbon-14 atom than in a carbon-12 atom?

None. Carbon-12 and carbon-14 are isotopes. They thus have the same number of protons, but carbon-14 has 2 more neutrons than carbon 12.

Online Chemistry Notes: Avogrados number and the mole (mol)

How many particles are in a mole (mol)?

1 mol = 6.022 x 1023 particles


(particles can be ions, molecules or atoms)

Note: sometimes this number may have a slight variation. For example some books may use  6.02 x 1023 or  6.02214150 x 1023

Online Chemistry Notes: Valence Electrons definition

1. Define valence electrons?

The electrons in the outer most shell of an atom. These are the electrons farthest away from the nucleus and are involved in bonding.

Online Chemistry Notes: SN2 Energy Diagram (Organic)

Here is the Energy Diagram for an SN2 reaction. You can see a strong nucleophile ( and sometimes it acts as a strong base) attacking a substrate with very little steric hinderence. At the same time, it kicks off a large electronegative leaving group. Enjoy:

Sn2 Energy Diagram

Online Chemistry Notes: Charges for Transition Metals

Sometimes we will need to know the charge of a transition metal to predict the products of an equation, or name a compound.

So I created a table of the different names, and charges for common transition metals that you can use to do your homework. Here it is:

Name	Symbol	Charge
Ferric    or Iron (III)	Fe (III)	+3
Ferrous   or Iron (II)	Fe (II)	+2
Stannic   or Tin (IV)	Sn (IV)	+4
Stannous   or Tin (II)	Sn (II)	+2
Plumbic   or Lead (IV)	Pb (IV)	+4
Plumbous   or Lead (II)	Pb (II)	+2
Cupric   or Copper (II)	Cu (II)	+2
Cuprous   or Copper (I)	Cu (I)	+1
Mercuric   or Mercury (II)	Hg (II)	+2
Mercurous   or Mercury (I)	Hg (I)	+1

Online Chemistry Notes: The Periodic Table

One of the first things you will have to do on your quest for mastering chemistry is memorize most of the elements on the periodic table!!!(oh no!) 

It's okay though, because after a certain amount of exposure to chemistry it just becomes natural. I have composed a complete table below for you to use as a resource. One column contains the chemical symbol of an element, and the other has it's name. Here it is:

H	Hydrogen	Fe	Iron	Te	Tellurium	Ir	Iridium
He	Helium	Co	Cobalt	I	Iodine	Pt	Platinum
Li	Lithium	Ni	Nickel	Xe	Xenon	Au	Gold
Be	Berylium	Cu	Copper	Cs	Cesium	Hg	Mercury
B	Boron	Zn	Zinc	Ba	Barium	Tl	Thallium
C	Carbon	Ga	Gallium	La	Lanthanum	Pb	Lead
N	Nitrogen	Ge	Germanium	Ce	Cerium	Bi	Bismuth
O	Oxygen	As	Arsenic	Pr	Praseodymium	Po	Polonium
F	Fluorine	Se	Selenium	Nd	Neodymium	At	Astatine
Ne	Neon	Br	Bromine	Pm	Promethium	Rn	Radon
Na	Sodium	Kr	Krypton	Sm	Samarium	Fr	Francium
Mg	Magnesium	Rb	Rubidium	Eu	Europium	Ra	Radium
Al	Aluminum	Sr	Strontium	Gd	Gadolinium	Ac	Actinium
Si	Silicon	Y	Yttrium	Tb	Terbium	Th	Thorium
P	Phosphorus	Zr	Zirconium	Dy	Dysprosium	Pa	Protactinium
S	Sulfur	Nb	Niobium	Ho	Holmium	U	Uranium
Cl	Chlorine	Mo	Molybdenum	Er	Erbium	Np	Neptunium
Ar	Argon	Tc	Technitium	Tm	Thulium	Pu	Plutonium
K	Potassium	Ru	Ruthenium	Yb	Ytterbium	Am	Americium
Ca	Calcium	Rh	Rhodium	Lu	Lutetium	Cm	Curium
Sc	Scandium	Pd	Palladium	Hf	Hafnium	Bk	Berkelium
Ti	Titanium	Ag	Silver	Ta	Tantalum	Cf	Californium
V	Vanadium	Cd	Cadmium	W	Tungsten	Es	Einsteinium
Cr	Chromium	In	Indium	Re	Rhenium	Fm	Fermium
Mn	Manganese	Sn	Tin	Os	Osmium	Md	Mendelevium
		Sb	Antimony			No	Nobelium
						Lr	Lawrencium
						Rf	Rutherfordium
						Db	Dubnium
						Sg	Seaborgium

The Good news is you DONT have to memorize ALL of them. Here is a list of the common symbols, to get you started, and even for this list you can focus on the blue symbols in the begining of the course:

H, He, Li, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ne, Cu, Zn, Ga, Ge, As, Se, Br, Kr, Rb, Sr, Mo, Pd, Ag, Cd, Sn, Sb, I, Xe, Cs, Ba, Pt, Au, Hg, Pb, Po, Rn, Fr, Ra, U, Pu

That's not so bad right?

and then there's this cool site...

http://www.buzzfeed.com/donnad/cartoon-elements-make-learning-the-periodic-table-fun?utm_term=.ehmdZJ1Ev&sub=2021532_879014#.ofonJVQzl


Good luck, and if you have any questions you can email CoolChemTutor@gmail.com