So, I bet you were sitting in class and heard your teacher say “Hey guys!  You get to memorize Polyatomic ions!”.  You don’t really know what they are, or how they interact with anything, all you know is, that guy writing on the chalkboard gave you a list of what seems like a dozen molecules to memorize.  So you think “Eh, that’s not too bad, its just formulas and names”, and then you realize…. THEY HAVE CHARGES TOO!!!

1. So, what are these … Things

Let’s break down the parts of the word: “Polyatomic”:

• Poly: means more than one.
• Atomic:  This means we’re dealing with atoms!  (Hydrogen, oxygen Lead, etc..)
• Ion:  Think back to when you learned what an ion was.  It is simply an atom with charge.  For example, the ion for Chlorine is Chloride (Cl^-), which basically means that it has a charge of -1.

Put it together and what do you have?  More-Than-One-Atom-with-charge.  This means that we have multiple atoms together that have an overall charge.  These guys basically act as a single unit together.  You can think of these as combinations of molecules as “Super Atoms”, because they act like a single atom, but are composed of more than one.  These “Super Atoms” behave just like any lone atom does, and it is important to remember that.

2. Forming Compounds with Polyatomic Ions

So now I bet your Chem teacher has told you that you’re going to have to be able to name polyatomic ions and make compounds with them?  Egh!  My advice to you is to read carefully, because if you have a tricky Chemistry teacher, it is easy to get disoriented.

Examples:

QUESTION 1:

What is the Chemical Formula for Sodium Phosphate?  (NOTE it is Phosphate, not Phosphide!  Chem teachers try to pull this on their students ALL the time!)

1. Write the formulas out for each compound and their charges next to it.

Sodium = Na¹⁺ Phosphate = (PO₄)^2-

2. Cancel Charge: We want our compound to be neutral, so we must ensure that we don’t have any leftover charge.  Here, it is easy because all we have to do is add three ions of sodium to cancel out the one polyatomic ion of Phosphate, because sodium’s charge is +1, and Phosphate is -3. So we need 3 Sodium ions.

3. Write the Formula (If you’re not familiar what the (aq) means, do not worry about it.  It is just stating that the compound is soluble in water.):

Na₃(PO₄)_(aq)

The following questions have answers at the bottom :)!

QUESTION 2: Write the chemical formula for Calcium Carbonate.

QUESTION 3: Name this compound:  NaNO₃(aq)

If there is any request, I will write a Polyatomic Ion quiz on the site.

3. Common Polyatomic Ion Table

4. Answers!

QUESTION 2: Ca(CO₃)₂ Calcium’s charge is 2+ and Carbonate’s is 1-.  We need two Carbonates to cancel out Calcium’s Charge!

QUESTION 3: Sodium Nitrate

I hope this was helpful!  I look forward to blogging more in the future!

When placing a large number into scientific notation:

1. Place the decimal point after the first integer in the number.
2. Count the number of integers after the decimal point.
3. Round to however many decimal places you’re required to.
4. Take your rounded number and write as (NUMBER x 10^integers ). You don’t have to include the parentheses.
5. Where you see the word integers, write the number that you counted in step 2.

.

Here’s a quick example:

• So, we want to put the number 759865783674748 into scientific notation with two places after the decimal.

• The first thing we’re going to do is to place the decimal after the first integer like this:   7.59865783674748

• After counting the number of integers that follow the decimal point, we find that there are fourteen.

• Now, we can round the number to two places after the decimal. Since “8″ is bigger than “5,” we can round up. We end up with 7.60 as the rounded number. You may be asking why we leave that zero there when zeros after the decimal aren’t usually written. When you’re specifically asked to write the number with two decimal places, it’s necessary to fill both of those places, even when it’s just with a zero.

• So, we have all of the pieces. All that we need to do now is to put them all together. Using the formula in step 4, we can arrange the information to get this as the final answer:

• 7.60 x 10¹⁴

.

Using small numbers rather than big ones:

• Now that you’ve seen how to write very large numbers in scientific notation, what about really small numbers? The whole point is to avoid writing out a lot of digits. Can’t that be used to write really small numbers too?

• Of course it can. In fact, let’s look at how to write the number 0.000000000003145 in scientific notation.

• This is really similar to what we did before. The only real difference is that in step 4, you’re going to write it as ten raised to the NEGATIVE number of integers.

• You’d think that we’d place the decimal first, just like last time, right? Not quite. If you place the decimal before you count the number of integers between where it is now and where you’re going to put it, how will you know how many integers there are!!?!?

• So, after counting the integers, we find that there are twelve between the decimal point’s start and end location.

• Now that we know this, we can move the decimal to it’s new location… AFTER THE FIRST ACTUAL NUMBER: 3.145

• Round to two places after the decimal: 3.15

• Now, we simply complete by putting all the information together: 3.15 x 10^-12

.

Hope this helps!

Grey

One of my favorites, other than those amazing croissants, is his fresh bread. I can’t give away the recipe, but let’s pretend for a second. Let’s say that my friend the baker gets commissioned to cater a luncheon for 24 people. They want him to make his bread, so he decides to be generous and prepare 12 loaves. (That’s a lot of bread when you think about the fact that each person gets half of a whole loaf.) Each loaf of bread requires 7 eggs. If you do the math correctly, you should find that the total number of eggs he’s going to need comes to 168 eggs… aaaaand ACTION!

.

Scenario 1 – Before the mole.

Back in his kitchen, my friend the baker has set aside ten extra minutes to check and recheck that he has the correct number of eggs. Why so much time? Because he has to COUNT THEM ALL BY HAND. They come in buckets with to set number in each bucket. He has to sit there and count eggs to 168… and hope that he doesn’t get distracted or lose count. By the time he get’s up to 76, the phone rings for the third time, and he loses count again… there HAS to be a better way…

.

Scenario 2 – Mole to the rescue.

Thankfully, eggs come in cute little packages of ONE DOZEN EGGS. There’s not much thinking involved. He knows that every time he reaches for a package of eggs, he’s getting 12. In his head, it only takes a second or two to calculate that he’s going to need 14 packages of eggs. It’s so much easier when there’s a system to make the counting easier. HINT HINT.

.

The mole in chemistry is pretty much the exact same thing. It’s just a way of grouping molecules together just like eggs. The only real difference is the size. Since molecules are so small and we are so big, we tend to use measurements that are humongous… try 6.0221415 x 10²³ items in a mole compared to the 12 items that are in a dozen.

It’s a good thing we don’t buy moles of eggs!!

.

1. Water is the most abundant chemical compound on the planet.

There are more water molecules in the breath you just took than there are people who you will EVER MEET IN YOUR LIFETIME. I can prove it.

There is one mole of water in every 22.4 liters of air at normal conditions. That means that there is approximately 5% of a mole in every liter of air. A normal human breathes about one half of a liter of air in every breath. That means that there is approximately 2.5% of a mole in every breath. Since one mole is 602,200,000,000,000,000,000,000 molecules, there are 15,100,000,000,000,000,000,000 little waters in every breath. There aren’t even half that many people alive right now.

2. Water can serve as a source of both Hydrogen and Oxygen.

If you know anything about biology, you know that without either of those elements, you wouldn’t last another hour. Both oxygen and hydrogen are necessary for running some of the most foundational cellular processes that keep you alive. A molecule that can give you both of those elements at the SAME TIME is a winner.

3. Water is a medium for almost all biological reactions.

If it happens, it happens in water. Water is just the “in” place among the cool chemicals.

But on a more serious note, water is a wonderful medium for chemical reactions because it allows solutions to be very dense. Much more dense than in air. If your body was to use air for a biological medium in the same way that it uses water, you would either be very very very large or you would always be in danger of EXPLOSION from the high pressure!

4. Water is usually inert/stable at normal Earth conditions.

Water is just smooth… and cool. It doesn’t need to go exploding all the time in order to make friends. It’s smarter than that.

For whatever reason, water has become the perfect conditions for water to exist at a fairly stable state. This means that it is possible for living organisms to use it without much risk of danger.

5. Water can hold tightly to large amounts of heat energy.

It takes a lot to get water all steamed up, but when he’s hot, he STAYS that way. Rawrr!

Water has a ginormous heat capacity, so it doesn’t change temperature very easily. It takes a lot of energy to heat water up, and water releases that heat very slowly. This is advantageous for animals especially because animals (humans included) are composed of mostly water… around 60%. The heat capacity of water makes it easier to control body heat because the water in your body doesn’t allow for rapid temperature changes.

6. Water was the habitat for life on Earth before land was.

Many scientists believe that there was a point, many millions of years ago, that all living creatures lived underwater. Of course, this was long before the Earth looked anything like it does today. Scientists think that the earth was once completely covered in water; eventually geological activity forced the sea-bottom up to the top, and land was formed.

If you’re living in water, fighting every other creature there just to stay alive or competing with everybody else to get access to food, you would have a much easier life if you could live on land. It is believed that some plants and animals were able to make the transition from water to land. Because land creatures were once aquatic, though, we still possess true needs for water as well as the ability to use water for biological reactions.

7. Water can act as both a base and an acid.

In most circles, the definition of an acid is any molecule that releases a lone hydrogen atom into solution, and the definition of a base is usually anything that can release a hydroxide ion. Since every reader of this article isn’t a biochem major, I’ll anabolize this for you.

You know that water is H2O, but that also means that it’s H-O-H. There are two hydrogen atoms and an oxygen atom. A lone hydrogen atom (H+) carries a positive charge that makes it very reactive; this charge causes the lone atom to be called an ion. Likewise, the other half of the water molecule (termed a “hydroxide ion”), carries a negative charge and is also very reactive. When either of these are very concentrated in a solution, they tend to make things happen… as far as reactions go. It gets much more complicated than I can really efficiently describe here, but trust me, the fact that water can do all of that is really significant.

8. Water is the Universal Solvent.

Ok, so everything in the universe can’t dissolve in water. In fact just today in chem class, I learned of a little trick chemists use to describe how much of a “non soluble” compound will actually dissolve. But that’s an idea for another post… and takes that idea in a completely opposite direction.

As far as animals are concerned, all of the necessary molecules are soluble. Water is the medium for ALL major body processes. It is used to regulate temperature and to be the medium for reactions throughout the body. It’s pretty darn significant… if you ask me.

.

But there’s not really any surprise there… water is Chuck Norris.

I talk too much, so here’s the lesson. Straight up.

Steps for Writing Lewis Dot Structures

1. Draw the molecular skeleton. As a rule of thumb, H atoms are always on the ends and the least electronegative atoms are in the middle.
2. Calculate the total number of VALENCE electrons that will be in the final molecule. You can do this by adding the group numbers of each atom together.
3. Distribute the electrons among the atoms. Start with the bonding atoms (2 electrons per bond) and then go back and fill in octets and duets where needed. Make sure you don’t add any more electrons than the number you calculated in step 2.
4. Make double or triple bonds when necessary. If any atom does not have a full octet, share a pair of electrons from a nearby atom in order to form a double or triple bond so that each atom can have a full octet.

Example: Sodium Fluoride

First, we’ll need to figure out the skeleton for NaF. Since there are only 2 atoms, there’s no need to consult a periodic table for electronegativity.

Next, we’ll need to add together the valence electrons to find out exactly what we’re working with here. Since Sodium is a Group 1 atom and Fluorine is a Group 7 atom, we know that the total number of valence electrons is (1+7)=8.

Now that we know how many electrons to work with, we’ll start by adding our bonding electrons.This leaves us with 6 electrons to distribute.

Distributing these last six electrons doesn’t give us enough to complete an octet.

So, let’s share the electrons so that we end up with two full octets. This means that we’ll have to use a double bond.

Best of Luck,

Grey

In chemistry, we are covering Lewis Theory. I was reading over the energies associated with chemical bonding when I ran across something that I found to be interesting: metals do not covalently bond. In fact, they have their own distinct form of bonding. I thought to myself “what a perfect post topic!”

If you think of yourself as a science nerd, then I’m sure that you’re very familiar with both Ionic and Covalent bonding. If not, here’s a Quick Review: Ionic = electron transfer, Covalent = electron sharing.

However, you may not be as familiar with metallic bonding. As a biology nerd by trade, I sure wasn’t familiar with this when I ran across it. I had always thought that a bond between metal atoms was just like a bond between nonmetal atoms. WRONG.

Allow me to introduce the “electron sea” model of metals. It’s just like it sounds: metal atoms float around in a sea of electrons. You could also think of it like creamed corn.

But what’s so different about this? In ionic and covalent bonds, any one electron is pretty much bound in place. It still moves around the nucleus of the atom or atoms that it’s bound to, but it never leaves. On the other hand, in the electron sea model of metals, the metal atoms stay in pretty much the same places, but their electrons are free to move from atom to atom as they please.

This model also explains the ability for metals to conduct electricity (electrons can flow from atom to atom) and malleability (the atoms are not glued into place. their electrons can flow, allowing changes in conformation).

Whereas ionic and covalent bonds are both rigid in their structure, metallic bonds are the most easy-going of the group. They just go with the flow… of electrons.

.

Best of Luck,

Grey

I have seen lots of definitions for this term– each more technical than the last. In essence, stoichiometry is the use of the ratio given in a balanced chemical equation. WHOA! He used the word “ratio.” That’s a scientific term, which breaks the rules of MPSN. This is supposed to be a site for people who just don’t get it. What the heck is this guy thinking?

Before you remove us from your bookmarks and badmouth us on forums, read on.

In an attempt to figure out how to boil this concept down to its most basic elements, I ran across Mr. Guch’s Great Big Vocabulary List. After laughing myself into convulsions, I realized that this is some pretty good stuff. You should check it out. But anyway, Mr. Guch defines stoichiometry as “The art of figuring how much stuff you’ll make in a chemical reaction from the amount of each reagent you start with.”

I couldn’t have said it better myself… so I didn’t. I instead quoted Mr. Guch. Is this becoming a little more clear now? Stoichiometry is figuring out how much A and how much B you need to get C… and then how much C you get. All this theory is starting to get a little cloudy, I’m sure. So let’s look at an example.

Take for example Aluminum Oxide. I’m sure that you can guess the two components of this compound: Aluminum and Oxygen.

Al + O₂ –> Al₂O₃

…but that’s not balanced…

4 Al + 3 O₂ –> 2 Al₂O₃

… now that’s balanced. But what does that really mean? If you’ve gotten this far in your study of chemistry, then you are familiar with the mole concept. That “4″ in front of the “Al” means that there are 4 moles of Al MOLECULES in this reaction. (It just kinda happens that a single aluminum atom can exist without being covalently bonded to any other atom.) The “3″ in front of the “O2″ means that there are 3 moles of O2 MOLECULES in this reaction. (Oxygen atoms, unlike aluminum atoms, cannot exist without being bonded to another atom. In this case, oxygen is bonded to another oxygen, thereby forming a gaseous oxygen molecule.) By now, you’ve already figured out that the “2″ in front of the “Al2O3″ means that the product is 2 moles of aluminum oxide.

BUT HOLD ON! Three moles plus four moles should give you SEVEN MOLES, not TWO!!! Sorry, but there’s no way to argue that. It’s just wrong. If you look more closely, you’ll see that the number of moles represents the number of moles of THAT MOLECULE, not the atoms that make it up. So, in this case, 4 moles of aluminum and 3 moles of oxygen only give us 2 moles of aluminum oxide.

Ok, so if you don’t learn ANYTHING ELSE FROM THIS ARTICLE, learn this concept. For every 4 moles of Al you put into the reaction, the most Al2O3 you can get out is 2 moles. For every 3 moles of O2 that you put into this reaction, the most Al2O3 you can get out is STILL 2 moles. THAT DOES NOT MEAN THAT YOU WILL ALWAYS GET 2 MOLES, it means that for every 4mol Al or 3mol O2, 2mol Al2O3 is the MAX that you can get in the end.

Stoichiometry Example Problem:

I’m going to give you 8 moles of Al and 3 moles of O2. What are your products going to be, and how much of each will you get?

Step 1: Limiting Reactant

Look at the balanced equation to see how many moles of product you could possibly get MAX from each of the reactants I gave you.

(8mol Al) x (2mol Al2O3 / 4mol Al) = 4 mol Al2O3

(3mol O2) x (2mol Al2O3 / 3mol O2) = 2 mol Al2O3

As you can see, although we have enough Aluminum to make 4 moles of product, we only have enough Oxygen to make 2 moles of product. So oxygen is our limiting reactant.

Step 2: Leftovers

That being said, all of the oxygen is going to be used up, and 4 moles of aluminum are going to be used up. (we know that just by looking at the balanced equation) This is going to leave you with 4 moles of Aluminum. So the final verdict is 4 moles of unreacted Al and 2 moles of Al2O3.

.

Best of Luck,

Grey

My Great-Great-Great-Great-Great-Great Grampappy just died, and he left me a mansion. I’m excited… umm, as well as mournful and emotionally destroyed… (wink). There’s still some paperwork to fill out before I can move in, but I decided to check out the place anyway. You know, since it’s technically mine anyway.

My sister and I took a drive out to see the house – magnificent. The architecture astounded me; it’s shaped like an upside-down pyramid. It was so beautiful, in fact, that my sister couldn’t help herself from darting from the car and through the front door. Two hours later, I had NO IDEA where she went. She called me on my cell phone to ask me how to get where I was. It took somewhere in the realm of two weeks for us to find each other, but I am happy to announce that we are both still alive and reunited.

You know, it’s too bad my sis and I didn’t know back then what I now know about quantum numbers. Why? Because quantum numbers are a system of identifying the location of an electron within an atom (or a sister within a mansion). Allow me to explain:

There are four quantum numbers that you really have to worry about (there are technically more, but in general chemistry, you only need to be familiar with these): N, L, Ml, and Ms.

Principal Quantum Number (n)

So, the first thing I would need to know if i wanted to locate my sister within the house would be what floor she was on. This would be especially helpful because I could eliminate a HUGE percentage of the house from the search if I could narrow the possibilities to a single story on the mansion.

As far as chemistry is concerned, the tool here is the principal quantum number, or “n” for short. The principal quantum number tells you which energy level that an electron can be found in an atom. Think about it like this: if n=3 for an electron, that electron is on the 3rd floor of the atom.

Azimuthal [Angular Momentum] Quantum Number ( l )

Well, now let’s assume that she’s on the third floor (n=3), but where on the third floor? There are HUNDREDS OF ROOMS up there!! It’s too bad there isn’t a way to tell what room she’s in…

Que chemistry again. The “Azimuthal” or “Angular Momentum” quantum number does just that. This number, represented usually by a lowercase L, tells you which shaped orbital the electron of interest is residing in. There are plenty of differently shaped orbitals, but you only need to know these:

• l=0, S-shaped orbital
• l=1, P-shaped orbital
• l=2, D-shaped orbital
• l=3, F-Shaped orbital

The shapes of the orbitals aren’t actually the same shapes as the letters S, P, D, and F. Those letters represent the shapes of the orbitals, which is a topic for another post.

But, think of the azimuthal quantum number as representing the room that the electron can be found in. For example: if n=2 and l=1, we know that the electron is in the second energy level, and it’s somewhere in the P orbital. In terms of my sister, she’s on the second floor and in the kitchen, as opposed to the second floor bathroom.

Since the house is shaped like an upside down pyramid, the number of rooms on every floor has to get bigger as you climb upstairs. In fact, it’s just one fewer than the number of the floor itself. So on the 100th floor, there would be 99 rooms! The angular momentum quantum number works just the same. In order to find out what it is, just subtract one from (n).

Magnetic Quantum Number (Ml)

So, now we’re going with sissy being on the second floor (n=2) and in the kitchen (l=1), but now where in the kitchen? It’s a mansion after all, and there is a pantry, a cooking space, and a dishwashing room. She could be in ANY of those places.

The Magnetic Quantum number tells us a little more about where the electron is. It also specifies how many electrons can fit in a certain orbital. Let me explain:

Sissy is in the kitchen, but she could either be in Ml= -1 (the pantry), Ml=0 (the cooking space), or Ml=+1 (the dishwashing room). She told me that she was getting a snack, so I think it’s safe to assume that she’s in the pantry (Ml=-1).

Think of the Magnetic Quantum number like that. It will be found in a range from negative angular momentum to positive angular momentum. Example: If l=5, then Ml can only be between -5 and +5.

This may not make since right away, but it’ll be more clear when you work with electron configurations.

Spin Quantum Number (Ms)

I have no idea how to tie this one in to the upside down pyramid story, so I’ll do my best to explain it in a way that’s easy to understand.

You may already know that no more than two electrons can be in the same subshell (you’ll understand it more in electron configurations)., but you may not know that they have to be spinning in opposite directions.

In order to really understand that, I would have to explain a lot more chemistry than I actually understand… so I would probably confuse you in the process. So just take my word for it.

Because there’s not really any point of reference in the atom, we simply denote the first electron as going one way (+ 1/2) and the other electron is going the other way (- 1/2).  It’s really that simple.

.

An Article by

Mitchell

.

Sidenote:

Hey nerds! This is Grey. I just wanted to throw in a link to a site that I found that gives a visual aid to electron configurations. Many teachers go over electron configurations at the same time as quantum numbers, so I thought this might be helpful.

Best of Luck!

When you break down science into its simplest form, you get a surprisingly simple process.

.

A Crazy College Party

.

A guy has his eye on a girl at a party. He watches this girl for some kind of trait, tendency, or anything else that might give him the opportunity to act. We all know how this story ends. It’s a 50/50 shot because it’s a well known fact that it is impossible to understand the opposite gender!

.

But that won’t stop men and women all over the world from trying again and again. And the same can be said for scientists. The overall goal of a scientist is to try to gain an understanding of how the universe works through observation and experimentation.

.

Back to the guy at the party. He sees the girl go to the bar for a drink, and seizes the moment to plant his signature pickup line, “So…how am I doing so far?” After walking away defeated, he decides he has a little more observing to do.

.

The sad truth is that scientists rarely start off any better. Science is really just trial and error. Or experiment, after experiment, after experiment. Fortunately, scientists have come up with a rough method for finding an understanding of the universe. This method, the Scientific Method, is used to form a rough idea into (hopefully) a scientific law that works every time.

.

An observation can be as simple as flowers blossoming in Spring.

. Take the guy left alone at the bar. He started out with an observation, made a guess about what would work best to get him where he wanted, and gave it a shot. His first observation, discovering that he needed to be with that girl, was called Identifying the Problem. In the world of science, this can be observing anything you don’t know about, from the rusting of metal to the way flowers grow. Our guy’s next step was making a guess as to what would happen if he planted that oh-so-beautiful pickup line. In science jargon, this educated prediction about the outcome of an experiment, based on all your previous observations, is called a Hypothesis.

.

Which brings us to our next step, experimentation! After the guy made the hypothesis that he would win the girl’s heart if he used his pickup line, he put his plan into action. His desperate attempt at a rendezvous can be roughly compared to the controlled series of events that scientists use to support or rule out their current hypothesis, also called experimentation.

The major difference between the party goer and a scientist is that a scientist keeps all of the factors in an experiment constant except two. The variable that the scientist chooses to change is called the independent variable. The other variable that changes is the dependent variable, which changes as an effect of changes in the independent variable. For the guy at the party, his independent variable was the pickup line and the dependent variable was the girl’s reaction. A different pickup line might have produced a different reaction from the girl. However, some things, like the girl, the guy, and the party remained the same each time he tried a new pickup line. These things that stay the same in every experiment are called the control variables. In other words, the scientist makes these factors stay the same by controlling the conditions of the experiment.

.

Regardless of whether the experiment works or not, a good scientist will always run it again. More trials of an experiment will produce more knowledge, and a more definite understanding about how something works. If this guy somehow got the girl with his pickup line, he would (in the name of science, of course) try the experiment again and again and eventually develop a theory about how to get girls at parties. The same thing happens to regular scientists. Their theories, supported or disproved in experiments, form a general explanation for the behavior of something in nature. Eventually, when similar observations provide evidence concrete enough, a theory can be upgraded to a scientific law. A scientific law is a statement that briefly states a fundamental principle about the universe that holds true in any situation. (In short, a scientific law is an observable fact.)

.

So looking back at our poor fellow at the party, we can assume that he knows the scientific method, and that he will continue to reform a hypothesis and try new experiments until he finally gets the girl, develops a theory on the tendencies of women, and publishes this as a scientific law. Some of us can only hope that his paper gets published soon…

.

The End.

An Article by Mitchell