Chemical Bonding

Chemical Bonding
Lewis Dot Structure/Electron placement
1. Use the valence electrons
2. Place the valence electrons around the symbol

EX: Nitrogen is 1s2 2s2 2p3, meaning that it has 5 valence electrons (Highest energy level=2, 2s2 & 2p3, 2+3 = 5)
This means that 5 electrons will need to be accounted for.

Covalent Bonds, a bond between two nonmetal atoms.
Bond length is the distance between two nuclei. Measurement between the radius of the bonding atoms is less than the sum of the radii added together.

More Complex Lewis Dot Problems...

Sulfur trioxide
SO3

Sulfur has 6 valence electrons
Oxygen has 6 valence electrons, but there are 3 oxygen, so 3x6=18
Sulfur valence + Oxygen valence = 24 e-
So we begin our structure...
                                        
                                       O
                                        l
                                O -  S - O
And notice that there are three bonds, making six electrons accounted for. (2 per bond)
So that means out of our 24 e- we need to account for, 6 are taken care of just by bonds. However, there are still 18 e- that are unaccounted for. So we continue, adding electrons to the Oxygen...
                                      . .
                                    : O :
                                 . .    l    . .
                                :O - S - O:
                                 . .         . .
HEY! It looks done. But it's not. Sure all 24 electrons are accounted for, but S only has 6 electrons, not 8. This means we can double bond an oxygen, and recognizing that there will be resonance, it will look like, and variations of this
                                      . .
                                    : O :
                                 . .    l    . .
                                :O - S =O
                                 . .         . .


If you need a better tutorial, or a little more explanation, click here.

                                        

Periodic Trends on the Exam

Periodic trends were on the exam, and when I saw the first question about them I freaked out. How was I supposed to know the answer to that? There's so many trends. But, I flipped over my handy dandy periodic table and wrote out the chart that I made for trends. THATS how I'm supposed to answer those questions. It took a lot of flipping back and forth of my periodic table to my chart, but I think ultimately that is what helped me the most on the exam. Point 1 for memorization.

Electron Configuration

Examples of electron configuration...
Li
1s2 2s1

O
1s2 2s2 2p4

Ar
1s2 2s2 2p6 3s2 3p6
OR Argon (looks like) [Ne] 3s2 3p6
http://www.chemistrytutorials.org/content/atomic-structure/electron-configuration
http://chemwiki.ucdavis.edu/Core/Inorganic_Chemistry/Electronic_Structure_of_Atoms_and_Molecules/Electronic_Configurations

Electrons

2 electrons with the same spin will never occupy the same orbital...
N=1 1 Sublevel 1s Max. 2e-
N=2 2 sublevels 2s 2p max. 8e-
N=3 3 sublevels 3s 3p 3d max. 18 e-
N=4 4 sublevels 4s 4p 4d 4f max 32e-
 AUFBAU- electrons enter orbitals of LOWEST energy FIRST
PAULI EXCLUSION- an orbital can only contain TWO electrons with opposite spin
HUND'S- within a sublevel electrons enter singly before pairing up
http://education.jlab.org/qa/atomicstructure_06.html

4 Levels of Organization

1) Principal Energy Level---School Building
How far away from the nucleus an electron can be found (n)
2)Sublevel---Floor Number
(s, p, d, f)
1st principal energy level has one Sublevel, 1s
The 2nd principal energy level has 2 sublevels, 2s and 2p
The 3rd energy level has 3 sublevels, 3s, 3p, 3d
4th and all subsequent principal levels n=4s, 4p, 4d, 4f
http://w

ww.edu.pe.ca/kish/grassroots/chem/electron.htm

Trends in electronegativity

Electronegativity of an element is defined to be the tendency of an atom to draw electrons toward itself when chemically combined with another element. There are no units for this electronegativity, but it is just to be used as a comparative tool. Larger electronegativities pull electrons to themselves when bonded with other elements. Noble gases don't count when looking at electronegativity. Otherwise, electronegativity increases ⬆️➡️ The periodic table. http://www.chemguide.co.uk/atoms/bonding/electroneg.html

Periodic Trends

Again, the best way that I learn is through visuals.
Electronegativity increases ⬆️➡️ On the periodic table
Atomic Radius increases ⬇️⬅️ On the periodic table
Nonmetallic increases ↗️
Metallic increases ↙️
Electron affinity increases ⬆️➡️
Ionization energy increases ⬆️➡️ On the periodic table
http://chemwiki.ucdavis.edu/Core/Inorganic_Chemistry/Descriptive_Chemistry/Periodic_Trends_of_Elemental_Properties/Periodic_Trends

What is ICE Box?

I missed the lecture on "Ice Box", but this is what I've learned so far. ICE stands for Initial Change Equilibrium. It's also easier for me to learn through visuals and example, so I mostly just have links of pictures to share. http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Equilibria/Le_Chatelier's_Principle/Ice_Tables
https://m.youtube.com/watch?v=tT-2xk9ZG_A

Equilibrium Help

Just a few extra help websites for equilibrium equations

http://scienceaid.co.uk/chemistry/physical/eqconstants.html

http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Equilibria/Chemical_Equilibria/The_Equilibrium_Constant/Balanced_Equations_And_Equilibrium_Constants_2

ACID BASE

For acid base reactions, it's important to know how to determine pH and pOH of solutions. Basically, you're just finding the H+ or OH- concentration of the solution.

EX: 

The pH of a 12.5 M solution of HCl

pH= -log [H+]

-log [12.5 M]

pH= -1.097

For more examples, click here

For more explanation, click here

For a video explanation, click here

Click here for a quick review