Chemical Bonding, Part 2

As our current chemistry pedagogue is currently unavailable, PinchofKCN is here to help you get through the inevitable test next week. This post is dedicated to the art of depicting the structure of bonds. Below is a nice graphic chart to help you know the values of electronegativity for our beloved elements.

Now for some simple hard and fast (yet arbitrary) rules for the kinds of bonds that are formed between two elements.
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

How to draw the structure of atoms and bonds will also be on the test, so scrutinize carefully. The below chart show the valence electrons of some elements.

You'll notice that the transition metals are omitted; that's because we won't be tested much on those. Also they vary and it's above our level, just like predicting the structure of certain bonds. If you're asked to draw one and not sure if it has a single, double, or triple bond, use your best guess. Try to make it symmetrical. You'll want to try and make all atoms have 8 electrons surrounding it. This goes for both covalent and ionic bonds. How are they different? See below. 

Covalent bonds are like this.

A line represents a single bond of two electrons.

Ionic bonds are like this.

Put brackets around it and the charge on the outside.

YES. THIS UNIT IS THIS EASY SO FAR. DON'T FAIL EVEN IF MS CHEN IS NOT HERE. OK?OK.

My Chemical Romance

Chemical Bonding Part 1

First, I would like to apologize to everyone to came to this blog for "My Chemical Romance", this blog is strictly about 2 types of chemical bonding not crazy death rock music...

                        Correct                                                                                           Wrong

Ionic Bonding

Tip: Positive atom joins with Negative atom, usually the combining of Metals and Non-metals.

If you have forgotten about which elements have positive or negative charges, go back 2 posts with an EPIC period table.  Atoms want to gain or lose electrons in their outer ring so it will have a full ring. Usually the Metals will lose/give their electrons to the Non-metals because they have a strong force and they need the electrons from Metals. Separate a Ionic Bond you say? Impossible you say? Not impossible! You can actually separate these bonds by using very high melting point. In the picture below, you can see Sodium will give the extra 1 electron to Chlorine = both atoms have a full outer ring!!!

Eg.

(Non-Polar) Covalent Bonding

Tip: Negative atom joins with Negative atom, the combining of Non-metals and Non-metals...

Usually it is just called Covalent Bonding(don't need the non-polar). Metal does not participate in Covalent Bonding. Same concept as Ionic Bonding, 2 elements sharing their electrons this time to yield a full ring of electrons. Some of you may wonder, how do these particles hold each other? Obviously not with glue, instead it uses intramolucular forces to hold the molecule. But what puts them together? Intermolecular forces. How do I remember them? Here are some bad examples, Intramolecular, think of Intra Muscular holding the molecule together RAWR. For Intermolecular, think of what you need to get a job, AN INTERVIEW. SEE WHAT I DID THERE? 

 

Eg. 

     

Here a video for the illiterate kids...

Trends

Every graph has a trend. Even the craziest most unorthodox graph that's composed of limitations of values and additions of multiple function has a trend, if you force it to have one.

Luckily for us, the trends of the periodic table are less difficult to decipher, and also less complex. So here they are, short and sweet.

• Metallic properties increase right to left, up to down
• Atomic radii increases right to left, up to down
• Atomic Size increases right to left, up to down
• The least reactive elements are groups 7 and 8. It increases in reactivity in both directions, increasing going down on the left side and up on the right side.
• The melting point is lowest on both sides of the periodic table and increases as it approaches the centre.
• Ionization energy increases going down to up and left to right. 
• Electronegativity increases going down to up and left to right

Not so bad is it? 

I hope you've enjoyed these bite-sized blogs, because we're getting tested on them next week. And for good luck, have a rabbit. 

Periodic BOREDOM!

If you're going by the above periodic table, you are so definitely screwed for chemistry.

Today we're going to make this short and sweet since nobody cares about history!
So, Gods know how many years ago, people thought the world was made up of four elements: Earth, Air, Fire, and Water. Of course, these old ancient people were WRONG. A fair number of elements were discovered in the 1800's, but nothing notable until Mr. Mendeleev came along, and created the elegant Periodic Table of Elements.

Jargon aside, this table organized elements so that common characteristics would reappear periodically. With rows being periods and columns being families, each family would have similar characteristics because they are separated by a period. Make sense? Well figure it out. This is a history lesson.
Mendeleev's table was in fact, so elegant, that it predicted and left gaps for elements that had yet to be discovered. Ever since, it has been infallible. And ever since, over 100 elements have been discovered and named. All we have to do is appreciate this. Oh and know all this since it'll be on the test. The below image also won't help you with that portion of the test.

Valence Electrons and 'many more'

Hello my friends. How are you all doing today? I hope you're doing well because I won't be keeping you company for a very long today. In fact, in a couple minutes, I will be gone. [FOREVER] Jokes. But intense gaming will accompany you through the long night. [cough, cough, the typical nightlife of PinchofKCN ↓]

Anyhow, let's get this over with. So Valence Electrons, you may have heard of this term before in your junior science class  and most likely you've forgotten every single *beep* about it. So please allow me to recap this over again for you. Sigh, you kids...

Valence electrons are electrons in the outermost shell of an atom in which it/they can bond/react chemically with those of other atoms to form molecules. 

There are two very, I mean VERY, simple terms that you might want to NEED to carve them into your brains. 

Closed shell is a shell that has been closed forever a shell that has the maximum number of electron that it can contain. Whereas, an open shell is a valence shell that has fewer number of electrons than its maximum capacity. 

I will now 'chuck' a couple examples at you to end my boring  super intriguing lecture. 

E.g. How many valence electron(s) are in sulphur (S)?

First, you either write sulphur in the electron figuration notation (long or short), you'll get:

              1s²2s²2p⁶3s²3p⁴              OR                 [Ne]3s²3p⁴

Now, since we're looking for the valence electrons, thus looking at he OPEN SHELL, that is the '3s²...' shell. 

The maximum number of electron in that shell is 8, but we only have 6. 6<8. Therefore, we have 6 valence electrons for atom sulphur (S). 

You want more practice? Sorry, no, and your words are not heard by our writers' committee. 

You want a joke again? Oops sorry, only some bad humored cartoon this time. 

You just love Holden Caulfield right?! What happened to Mr. Spencer? That curly top-knot sure looks real to me. 

Kids!! Stop jumping up the stairs when you're excited!

Welcome back to PinchOfKCN's lesson! Are you currently enjoying your long-long four day weekend? Today we are very fortunate to have Professor Snape teaching us Chemistry, and as we all know, he is an excellent potions master; I'm sure you will like his lesson. As I can see, you guys are all very EXCITED, jumping up and down. But I should warn you that you may not want to upset Professsor Snape, or else he'll hit you in the head without mercy.
Back to today's lesson, our topic of the day is "the electronic structure of the atom", which means, we are going to find out how electrons in a certain element distribute themselves, as well as how many of them are circling around in their orbital.

Energy / Orbital Levels
When you are a kid, have you ever upset your mom because you never sit on a chair quietly? And perhaps your mom would then be so angry and suspect that you have Hyperkinetic Disorder? Well, this is what happens to an electron with high a energy level. When one or more electrons have energy levels greater than their ground state (lowest possible energy levels), they will jump up to a higher orbital level. (The energy level is represented by "n").

There are four types of orbitals, they are each referred by a different alphabet, s,p,d and f.

On the right, you can see the chart of electron configuration, starting with 1s, it is the first energy level. In different energy level, there will be a set of orbitals which allow electrons to occupy:
Level 1 (n=1): s type
Level 2 (n=2): s and p type
Level 3 (n=3): s, p and d type
Level 4 (n=4): s, p, s and f type

Here's a sample question: What is the electron configuration of the element Calcium in it's neutral state?
First, you will have to determine how many electrons in calcium. Look at your trusty BFC (a.k.a. Periodic table), and you should be able to tell it has 20 electrons. (If you are not able to get that number, then I'd say you were not paying enough attention during Ms.Chen's chemistry class)
Next, start filling in each orbital until you've "used up" all the electrons.
The following is a list of orbitals that each subshell has (note: the number inside the brackets=number of orbital):
1s(1), 2s(1), 2p(3), 3s(1), 3p(3), 3d(5), 4s(1), 4p(3), 4d(5), 4f(7)

Electron configuration for calcium:
1s2,2s2,2p6,3s2,2p6,4s2

Core notation can be used to simplify configuration writings, we use a set of the nearest noble gas element to represent Chemistry teachers claimed that they can help make things easier, but I think it just confuses us even more.
Here's a sample question:
Write the configuration using core notation for the element Potassium.
As you all know, potassium has 19 electrons, and if we have to write it's configuration without core notation, it'll be 1s2,2s2,2p6,3s2,3p6,4s1.
But now, we would like to simplify it, so we'll find the noble gas which has the nearest number of electron as potassium. Yes, it is argon. Argon has 18 electrons, and potassium has 19. So, we'll replace the configuration of 18 electrons with the symbol [Ar]. As a result, the final answer would be [Ar] 4s1.
Easy? Nah~ I'd say no. The hard part about core notation is that you'll have to figure out the remaining electrons AND transform it into configuration.

Now, it seems like the following three handsome guys have something important to say, and these are the concluding rules that you'll have to remember when writing configurations:

The Pauli Exclusion Principle

In 1925, Wolfgang Pauli proposed this principle to describe the arrangements of electrons in an atom. He suggested that protons and neutrons always obey the same rule, where electrons do not, where a certain amount of electrons can be placed in a given quantum state. Which is, in every given energy level, only a limited number of electrons can be placed. And in fact, he's right. Each orbit can have up to 2 electrons. If Pauli is wrong, then all the electrons will be pilling up in the first energy, which is, obviously impossible. Pauli also proposed  no two electrons can occupy the same state inside a closed system. (state=properties of an electron)

The Aufbau Principle
Our trusty Mr.Pauli did not only propose the exclusion principle; along with the famous Niels Bohr, they together created the Aufbau Principle (Also known as the "Application of quantum mechanics to molecular construction"). This principle suggested that lower energy level orbits should be filled before those of higher energy levels, where electrons should be added to an atom or a molecular system, and they will be interacting with the existing protons and neutrons.
(Side note: the word "Aufbau" means "building out" in German)

The Hund's Rule
Friedrich Hund propsed a law that every electron will only pair up when the previous orbital is fully occupied, and they will pair up with electrons with similar energy (aka: degenerate)

So that's pretty much all about electron configuration.
Confused? Huh? Well I'd say you're a genius if you are not. So here's a secret trick for you to find the electron configuration of any element very very easily.
But please do not leak the trick, or else it won't be a secret anymore, will it?
First, you will have to memorize know the distribution of different energy levels. A periodic table is shown below:

Then, let's say, you want to find the electron configuration for the element Sulfur. First, figure out how many electrons do carbon have. By look at your BFC, you will get the number 16.
Next, count horizontally, the number of elements on each row, until you reach sulphur. In this case, on the first row, there are 2 elements, hydrogen and helium. They both belong to the s-type orbital. As a result, we will write down "1s2".
Then go on to the second row, there are 2 s-type elements and 6 p-type elements, so you'll write "2s2, 2p6". Same for the third row, there are 2 s-type elements and 4-p type elements until you reach sulphur, so you'll write "3s2, 3p4". Combining the configurations above, you'll get "1s2,2s2,2p6,3s2,3p4".
Easy? Yes, I think it is.
Well, that pretty much wraps up our lesson for today, I'll wish you a happy long weekend and a good luck, because I, Sybill Trelawney, the professor of Divination at Hogwarts School of Witchcraft and Wizardry, predicts that you guys will be having a quiz or test very soon.

Friendly reminder:
Do not forget about your chemistry research project on the scientists as well! ;)
(Warning: This is NOT a joke)

PinchofKCN is back! Now with 10% more content and 50% more bad humour.

Hello everyone, miss us? Well I didn't miss you. Honestly, it was a great month not having to write a single darn thing for you little...erm, that is, we are coming out of hiatus, and with a new topic to boot. Welcome back!

Atomic Structure
Now as we all know, everything in the observable universe is made up of teeny-tiny round things, called atoms. What makes up atoms you ask? Well, mostly nothing. I'm not even kidding when I say it's 99.9999999999999% empty space. Shocking, isn't it? To know that everything you see could probably fit inside your pocket if completely compressed. Well, in chemistry, we don't care about that, so let's move on to the "important stuff".

Most of the mass of an atom lies in its nucleus, where the neutrons and protons are snuggled cozily together. Outside this central mass floats an electron cloud. Electrons orbit the nucleus in this cloud. In fact, they do this in such an odd way, it is impossible to determine the location of an electron at any given moment. This is quantum theory, and if you want to find out more, read the newspaper article I've yet to write. (Basically they "teleport" around in the electron cloud.)

Now that you're familiar with these subatomic particles, let's see what the purpose of their non-sentient existence is.

Electrons
The particles most easily gained and removed are called electrons, which are negatively charged. Along with protons, these particles determine the charge of an atom. Actually, once an atom has lost or gained electrons, it is called an "ion."

Typically, metals give off electrons and non-metals take electrons. You can imagine the metals as boys because they always give — I'm going to stop before I make an outrageously sexist comment. Moving on!

Negatively charged ions are called onions anions and are formed when electrons are gained. On the other hand, positively charged ions are called cats cations and form when electrons are lost. Please note that ions aren't necessarily individual elements! A compound can be charged too!

Neutrons
Neutrons (a particle without a charge), along with protons, give an atom its weight. Now, atoms, even those of the same element, don't all have the same weight. If your typical Carbon-12 atom, say, gained a couple of neutrons, it would become Carbon-14; the same element, just a bit heavier. There's nothing wrong with being Carbon-14, of course, but it would put that particular atom in a world where Carbon-12 reigns.

Why do atoms have different weights? The simple answer is because some are more stable. With all those neutrons and protons fighting for space, a little nudge will send a neutron flying away. Atoms with different weights from what is most common for their element are called isotopes. A well-known example is Uranium-235, used for nuclear bombs due to their instability.

Protons
What makes an element an element? The answer is protons (positively charged, you know, "pro"). A hydrogen atom has one proton; Carbon has 6, Nitrogen has 7. The atomic number of an element is also the number of protons it contains. What do you think happens when an atom gains or loses a protons? BAM, element change. This is alchemy, what those crazy bearded guys in ancient Greece and Egypt tried to do. (Well they just wanted to make gold, actually). Little did they know, alchemy is impossible with chemical processes. And we're honestly wondering why physicists laugh at us?

Conclusion
Well that wraps it up for this blog post! If you have any questions, ask the teacher. Seriously, learn to ask questions instead of sitting there and watching your grade point average steadily drop. We'll be back whenever, with whatever, written by whomever.

What's that? You want a joke? No.