When atoms are bonding, they ofter bond with some angles. A simple theory that enables the chemist to correctly predict the geometries of most substances is the valence-shell-electron-pair-repulsion-theory. We can say that as VSEPR.
Basicly VSEPR will have three situtions.
1, Three atoms. Example BeCl2
Cl----Be----Cl In this example, we calculate the angle between two non central atoms with the central atom. Therefore the angle betwee Cl and Cl is 180. We call it LINEAR shape.
2, Four atoms. Example BF3
F F
\ /
B
/
F The angle between F and F is 360/3=120
We call it Trigonal planar.
3, Five atoms. Explam CH4
H
/
H--C--H
/
H This one is special. When five atoms are bonding with a central atom. The angle will be 109.5
Alright guys, this is gonna be Organic Naming - last blog of the year :)
Alkanes + Alkene + Alkyne
Contain the carbon chain with:
Alkane has single bond (replace "e" with "ane")
Alkene has double bond (replace "e" with "ene")
Alkyne has triple bond (replace "e" with "yne")
How to name:
Count the longest carbon chain and come up with their name. ( methane, ethane ... )
Find out if there's any branch attached to the chain
Put the number indicates the branch's location in the carbon chain with the branch's name. Example: the methyl group locates in the 3 carbon of the chain --> 3-methyl
If there are more than 1 group then remember to put them in alphabetical order
If there are more than 1 same group at the same location, put their number of location including di, tri, tetra, penta ... Example: there are 2 methyl group at carbon 4 of the chain --> 4,4-dimethyl
Combine it with #1
Example:
Here we see that the longest chain has 4 carbons with single bond --> butane
there's a methyl group at carbon #2 --> 2 methyl
==> 2-methyl butane
Halides (Halogen) and Nitro
Halides and Nitro are group that has halogen element as a branch or NO2 (nitro) as a branch
How to name:
Follow exactly the rule above
Replace the ending of the element's name with "o"
Br = bromo
Cl= Chloro
F= Fluoro
I= Iodo
NO2 = nitro
Alcohols
An alcohol is an organic compound that contains (-OH) functional group
How to name:
Use the longest chain that contains -OH.
Replace the ending "e" by "ol". Example : Ethane --> Ethanol
Remember to make sure that you're in the lowest number and alphabetical order
Example:
We can see that the longest chain is ethane and -OH is in the first C --> no need to write number
--> the compound's name would be Ethanol or 1-Ethanol
Properties:
The -OH is an alcohol makes this compound soluble in water but then the hydrocarbon chain tends not to solute in water
And boys, alcohol is poisonous lol!
Aldehyde and Ketone
Both are contain carbonyl ( =0 )
Aldehyde
Aldehyde has the double bond O at the beginning of the chain.
How to name:
Find the longest chain of carbon, replace "e" by "al"
Make sure that you're in the lowest number and alphabetical order
Example:
We can count that the longest chain that contain =O has 8 carbon --> Octane
But because of the =O --> replace "e" by "al" --> Octanal
There's no more branch so our compound name would be Octanal
Ketone
Ketone is basically the same as Aldehyde but it contains the =O anywhere in the middle of the chain.
How to name:
Find the longest chain of carbon, replace "e" by "one"
Make sure that you're in the lowest number and alphabetical order
Example:
We count the longest chain that contains =O has 4 carbon --> butane
But the =O locates in the 2nd carbon of the chain --> it's an Ketone --> change Butane --> Butanone
Properties of Ketone and Aldehyde
Both are soluable
Aldehydes are very reactive, easily converted to Carboxylic Acids
Ketones are relatively unreactive
Carboxylic acids
Carboxylics are formed by and (=O) and (-OH)group
How to name:
Follow the basic naming
Replace the "e" in the longest chain by "oic" and "acid" at the end
Make sure that you're in the lowest number and alphabetical order
Example:
The longest chain has 4 carbons --> butane
There's the (=O) and (-OH) branch attached --> it's an Carboxylic acid
There's also the Chloro branch in the 3rd carbon and methyl brach in the 2nd carbon
The compound's name would be 3 chloro 2 methyl butanoic acid
Properties:
Carboxylic acids can be neutralized with a base
Ester
Easters are basically the combination of Carboxylic Acids + Alcohol
How to name:
Follow the basic naming rules
Name the R' carbon chain first as normally ( methyl, ethyl ... )
Then name the R carbon chain and replace an "e" ending with "oate"
Example:
We can see that the R' carbon chain has 3 carbons --> propyl
The R carbon chain has 1 carbon --> methane but it's an esters --> replace an "e" with "oate"
==> Propyl methanoate
Properties:
Ester have pleasant, fruity odors ...
Ethers
In ethers, Oxygen connects to 2 alkyl chain
How to name:
We follow the basic rule for naming
Name the short chain first then the longer chain second
The longer chain would be at last of naming ( basically alkyl )
The shorter chain would be named at first, replace "e" by "oxy"
basic ethers is methoxy methane
Example:
Properties:
Highly flamable
Insoluable in water
Good solvent for organic compound
Amines
Nitrogen bonds to H
How to name:
Follow basic naming rules
Add (-amino) with it's location in the carbon chain
Ending with the longest carbon chain ( methane, ethane ..)
Example:
The longest carbon chain has 5 carbon --> pentane
The amino branch locates in the second carbon of the chain -> 2 amino
==> 2 amino pentane
Properties:
Soluable
Fishy odors
Amines are organic base that easily form salts when react with acid
Alicylics
Use the same rule as Alkane and Alkene, just need to add "-cyclo" in front of the longest chain's name
The structure is gonna be ring, so depends on how many C in the longest chain, we would draw the appropriate ring
Example:
The ring has 6 carbons --> hexane
there are 3 methyl branches at location 1,2,3
=> 1,2,3 trimethyl cyclohexane
Note: If there's a double bond or triple bond, have to start counting from the beginning of the double bond or triple bond so we can get the lowest number.
Aromatics
Is the ring that contain benzene.
Follow same rule as alicylics
If benzene appears as a branch, add "phenyl" otherwise just add benzene at the end of your compound's name
Ex: 1,2,3,4 tetraphenylpentane
Ex: 1,2 dimethyl benzene
NOTE: All of the naming must be in the lowest number and alphabetical order
Okay, most of you know the Bohr Model... right? Well Lewis models are sort of like Bohr Models but with only the valence electrons around them. Valence electrons are.... Electrons in the outermost shell of an element or atom. Also called the "reactable electrons."
Sometimes Lewis diagrams are called dot structures because the diagram is made of dots, obviously.
So how do you draw a Lewis/ Dot Diagram? Step One - What element are you drawing?? Count the electrons. Step Two - Place the valence electrons around the element symbol.
Covalent bonds (Non- Polar Covalent bonding) - when electrons are shared EQUALLY. Bonding between non-metals (negatively charged).
Ionic bonds (Polar Covalent Bonding) - when 1 atom has a greater attraction for the electrons than the other atom. Bonding between non metals and metals
Electronegativity - the attraction of an atom towards its shared pair of electrons in a chemical bond.
^ Use me to help you understand more about electronegativity!!
To learn more about chemical bonds, check out these websites!
Hello, and today in class we have discussed Electronegativity. Now what is this large word?
Electronegativity - A measure of the tendency of an atom to attract electrons from a neighbouring atom.
After reading this definition, you may be wondering, what does that mean??? Well, here is a chart to help you understand better of what it means.
According to this chart, electronegativity values are much more higher at the family of noble gases, and on the far left of the table, the electronegativity is the weakest.
The formula for determining how high the value is, is to use the equation: |value| = |energy1 - energy2|. Notice the absolute value bars. Those indicate that the value will always be positive.
Here are some rules to follow:
1. Non-Polar Covalent bonds are formed when the difference between the values is less than 0.5 2. Covalent bonds are formed when the difference is between 0.5 and 1.8 3. Ionic bonds are formed when the difference is over 1.8
Lets do an example: Hydrogen and Fluorine.
Hydrogen's value is 2.2 and Fluorine's value is 3.98.
3.98-2.2 = 1.78.
These two are covalent bonds because when formed, the difference is between 0.5 and 1.8!
Here is a video, if you guys still do not understand. Enjoy!
HELLO! HOW YOU DOING! Okay, so today we went to the lab and discovered different types of trends using Microsoft Excel.
BACKGROUND
In 1870, Dmitri Mendeleev first proposed a new of studying and organizing the then known 63 elements. The modern form of the table has been modified and improved many times since Mendeleev's tables. Pioneers like Moseley(1913) and Seaborg(1941) have made the properties of the elements much simpler to study and understand.
Brief summary through definition and some new vocabulary:
Energy level: the amount of energy that electron can possess.
Ground State: it is when all the electrons are in lowest energy level.
Excited State: when electrons are in the energy level that different from the lowest level
Orbital: is the region, like the milky way surrounding around the nucleus that electron occupies in particular energy level
A shell: is the set of all the orbitals have same energy levels
Sub-shell: is the set of orbital of the same types (s,p,d,f)
Electron Configuration: is the notation that describes the orbital in which electron occupies and the total number of electron each orbital
Or this
Actually, i find the first chart easier to count and do exercise but its up to you. Here's how -> Usually in test you will be given question like this: Given element Na, write the electron configuration. Don't freak out yet, follow these steps !
Look into your periodic table to find that element. In this case, we found Na located in Group IA, period 3
Then find the element's proton's number, usually in the top left in the box
We all known that if the element is not ion, the number of electron = number of proton
So we will be able to know how many electron are there in the element. Okay keep in mind that number.
then we follow the route on the periodic table from left to write, top to bottom
So finally we just follow that route till we reach that element
I can write without think of anything: 1s2 2s2 2p6 3s1
Oh snap i forgot to mention the core notation. Arr i hate chemistry name so much, the core notation is basically the short form of the electron configuration that is easier and faster to write. Its in the form of [X] s(x) p(y) ... Here are steps:
Follow steps 1 above
Look backward to the previous row, then find the noble gas ON THE BACK ON YOUR ELEMENT, NOT IN FRONT OF
Write that noble gas in bracket in this case [Ne]
Then continue to write the electron configuration till you reach your element. => [Ne] 3s1
Here are some scientist contributed to this concept
The Pauli Exclusion Principle: in every given energy level, each orbit can only contains 2 electrons
The Niel Bohr Principle: electron exists in a specific energy states and can be filled up from low level to high level
Hund Rule: the Hund rule states that electron don't pair up unless they have to, that means they will fill out 1/2 the orbit first.
Valance Electron:
It's basically the number of electron in the outer most shell. Or orbital
Ex: The Valance Electron of Na ( [Ne] 3s1 ) is 1 cause there's only 1 electron in the outer most shell
