Writing Ionic Formulas: Introduction

Summary

This video explains how to write chemical formulas for ionic compounds by balancing charges between metals and nonmetals. Using examples like Lithium Oxide, Potassium Nitride, and Sodium Chloride, the process involves finding the elements on the periodic table, identifying their charges, and balancing them to form the correct formula. The video also highlights common mistakes, such as adding unnecessary numbers or retaining charges in the final formula. By the end, viewers will understand how to balance charges and write correct ionic compound formulas.

Takeaways

• 🔍 The first step in writing chemical formulas for ionic compounds is finding the elements on the periodic table.
• ⚡ Ionic compounds consist of a metal and a nonmetal, and their atoms have charges.
• 🧲 To write a chemical formula, it's essential to balance the positive and negative charges of the ions.
• 🔢 Use subscripts to indicate how many atoms of each element are needed to balance the charges.
• ❌ Do not add a subscript of 1 after an element's symbol, as it is implied.
• 🔄 When writing the final chemical formula, remove any charges from the symbols.
• 🔬 Lithium Oxide (Li2O) requires two lithium ions to balance one oxygen ion.
• 🔗 Potassium Nitride (K3N) requires three potassium ions to balance one nitrogen ion.
• 🧂 Sodium Chloride (NaCl) balances with one sodium ion and one chloride ion, making a simple 1:1 ratio.
• ⚖️ Aluminum Oxide (Al2O3) requires two aluminum ions and three oxide ions to balance the charges.

Q & A

What is the first step when writing a chemical formula for ionic compounds?

The first step is to identify both elements in the compound using the periodic table.

What type of compound is formed between a metal and a nonmetal?

A compound formed between a metal and a nonmetal is an ionic compound.

How can you determine the charge of an atom in an ionic compound?

You can determine the charge of an atom by looking at the column it resides in on the periodic table.

Why is it important to balance the charges when writing a chemical formula?

It’s important because the overall charge of the compound must be neutral, meaning the positive and negative charges need to balance each other out.

How do you balance the charges in a compound like Lithium Oxide (Li2O)?

Lithium has a +1 charge, and Oxygen has a -2 charge. To balance, you need two Lithium atoms (+1 each) to balance the -2 charge from one Oxygen atom.

What is the correct chemical formula for Potassium Nitride and why?

The correct formula is K3N. Potassium has a +1 charge, and Nitrogen has a -3 charge. You need three Potassium atoms to balance the one Nitrogen atom.

Why do you not include a number when only one atom of an element is present in the formula?

You don’t include a number when there’s only one atom because it’s understood that the element appears once if no number follows it.

What is a common mistake when writing chemical formulas, and how can it be avoided?

One common mistake is writing a number '1' after an element (like LiO1). This is incorrect; instead, write the element without a number if only one atom is present.

Why should you remove the charges when writing the final chemical formula?

You should remove the charges because the chemical formula only reflects the ratio of atoms, not their individual charges.

How do you write the formula for Aluminum Oxide (Al2O3)?

Aluminum has a +3 charge, and Oxygen has a -2 charge. To balance the charges, you need two Aluminum atoms (+6 total) and three Oxygen atoms (-6 total), so the formula is Al2O3.

Outlines

00:00

🔬 Introduction to Writing Chemical Formulas for Ionic Compounds

This paragraph introduces the concept of writing chemical formulas for ionic compounds. It starts by explaining the process of converting chemical names, like Magnesium Chloride, into formulas like MgCl2. The first example given is Lithium Oxide, where the periodic table is used to identify the elements and their charges. The distinction between metals and non-metals is emphasized, explaining how Lithium (Li) and Oxygen (O) form an ionic compound. The process of balancing charges by adding more Lithium atoms to equalize the charges is described, resulting in the chemical formula Li2O.

05:02

🧪 Potassium Nitride Example: Balancing Charges

This paragraph explores the process of writing the chemical formula for Potassium Nitride (K3N). The periodic table is used to identify the elements and their charges, with Potassium having a +1 charge and Nitrogen having a -3 charge. To balance the charges, multiple Potassium atoms are added, resulting in three Potassium atoms balancing the charge of one Nitrogen atom. The correct formula, K3N, is derived by writing how many of each atom are needed for the charges to balance.

10:03

🧂 Sodium Chloride: A Simple Ionic Compound Example

The process for writing the formula for Sodium Chloride (NaCl), a common example of an ionic compound, is explained. Sodium (Na) has a +1 charge, while Chloride (Cl) has a -1 charge. Since the charges are already balanced with one Sodium and one Chloride atom, the formula is written as NaCl without additional numbers. The ease of balancing charges for this compound is highlighted.

⚗️ Aluminum Oxide: A Tricky Compound

Aluminum Oxide (Al2O3) is presented as a more complex example. Aluminum has a +3 charge, and Oxygen has a -2 charge, making it necessary to add multiple atoms of each element to balance the charges. The paragraph explains the process of balancing the total charges by adding two Aluminum ions and three Oxygen ions, resulting in the formula Al2O3. The complexity of balancing charges in this example is emphasized.

🚨 Common Mistakes in Writing Chemical Formulas

The final paragraph highlights two common mistakes students make when writing chemical formulas. The first mistake is adding a '1' after elements, which is unnecessary and incorrect (e.g., Li2O1 is wrong; it should be Li2O). The second mistake is leaving the charges in the chemical formula, such as writing Li+2O2-, which is also incorrect. The correct approach is to remove the charges and simply write Li2O. The importance of avoiding these errors is stressed.

Keywords

💡Ionic Compound

An ionic compound is a chemical compound composed of positively charged ions (cations) and negatively charged ions (anions) held together by electrostatic forces. The video emphasizes that ionic compounds are formed between metals and nonmetals, as seen in examples like Magnesium Chloride (MgCl2) and Lithium Oxide (Li2O). These compounds must balance positive and negative charges to achieve a neutral overall charge.

💡Periodic Table

The periodic table is a tabular arrangement of chemical elements, organized by increasing atomic number, electron configuration, and recurring properties. In the video, the periodic table helps identify the charges of elements based on their columns, which is crucial for determining how to balance the charges when writing chemical formulas for ionic compounds. For instance, Lithium (Li) is in the +1 column, while Oxygen (O) is in the -2 column.

💡Metal

Metals are elements that tend to lose electrons and form positive ions (cations) in chemical reactions. In the video, Lithium, Potassium, and Sodium are examples of metals that combine with nonmetals to form ionic compounds. Metals are always found on the left side of the periodic table and are essential in creating the positive charge needed to balance the ionic compounds.

💡Nonmetal

Nonmetals are elements that tend to gain electrons and form negative ions (anions) in chemical reactions. In the video, Oxygen, Nitrogen, and Chlorine are nonmetals that pair with metals to form ionic compounds. Nonmetals are located on the right side of the periodic table, and their negative charge balances the positive charge of metals in ionic compounds.

💡Charge

Charge refers to the electric property of ions, either positive (cation) or negative (anion). In the video, the charge of each element is identified based on its column in the periodic table, such as +1 for Lithium (Li) and -2 for Oxygen (O). Balancing these charges is essential for writing correct chemical formulas for ionic compounds, as seen in examples like Li2O, where two Li+ ions balance one O2- ion.

💡Balancing Charges

Balancing charges involves adjusting the ratio of cations and anions in an ionic compound so that the total positive and negative charges are equal, resulting in a neutral compound. In the video, this process is demonstrated with examples like Potassium Nitride (K3N), where three K+ ions balance one N3- ion, ensuring the compound is neutral.

💡Lithium Oxide (Li2O)

Lithium Oxide is an example of an ionic compound discussed in the video. It is formed by combining two Lithium (Li) atoms, each with a +1 charge, with one Oxygen (O) atom, which has a -2 charge. The correct chemical formula, Li2O, represents the balance of charges required to create a neutral compound, with two positive charges from Lithium balancing the two negative charges from Oxygen.

💡Potassium Nitride (K3N)

Potassium Nitride is another ionic compound example in the video. It forms by combining three Potassium (K) atoms, each with a +1 charge, with one Nitrogen (N) atom, which has a -3 charge. The correct chemical formula, K3N, reflects the need for three Potassium atoms to balance the charge of one Nitrogen atom, ensuring neutrality.

💡Sodium Chloride (NaCl)

Sodium Chloride, commonly known as table salt, is a simple ionic compound discussed in the video. It consists of one Sodium (Na) atom with a +1 charge and one Chloride (Cl) atom with a -1 charge. Since the charges are already balanced with one of each atom, the chemical formula is simply NaCl, with no need for additional atoms.

💡Aluminum Oxide (Al2O3)

Aluminum Oxide is a more complex ionic compound mentioned in the video. It forms by combining two Aluminum (Al) atoms, each with a +3 charge, with three Oxygen (O) atoms, each with a -2 charge. The correct chemical formula, Al2O3, balances the six positive charges from Aluminum with the six negative charges from Oxygen, creating a neutral compound.

Highlights

Introduction to writing chemical formulas for ionic compounds, starting with names like Magnesium Chloride and deriving formulas like MgCl2.

Identifying elements on the periodic table as the first step, focusing on Lithium (Li) and Oxygen (O) for Lithium Oxide.

Explanation of the periodic table separation: metals on one side, nonmetals on the other, and the significance of the 'staircase' as a divider.

Definition of ionic compounds as those formed between metals and nonmetals, involving atoms with charges.

Determining the charge of elements based on their position in the periodic table, with Lithium having a +1 charge and Oxygen having a -2 charge.

Balancing charges in compounds by adjusting the number of atoms: for Lithium Oxide, 2 Lithium atoms are required to balance 1 Oxygen atom.

Writing chemical formulas by specifying the number of atoms needed for charge balance, resulting in the formula Li2O for Lithium Oxide.

Explanation of Potassium Nitride formation, showing Potassium (K) with a +1 charge and Nitride (N) with a -3 charge.

Balancing charges for Potassium Nitride requires 3 Potassium atoms to balance 1 Nitride atom, resulting in the formula K3N.

Sodium Chloride (NaCl) example, showing that a +1 Sodium ion balances with a -1 Chloride ion, making the formula straightforward as NaCl.

Detailed example of Aluminum Oxide (Al2O3), showing how two Aluminum atoms (+3 charge each) balance with three Oxygen atoms (-2 charge each).

Common mistake: Writing 'O1' or similar unnecessary subscript for single atoms, which should be avoided.

Another common mistake: Including charges (e.g., Li+2O2-) in the final chemical formula, which is incorrect. Charges should be omitted in the formula.

Reminder to balance charges for each compound and ensure the chemical formula reflects the smallest whole number ratio of atoms.

Encouragement to practice more problems or explore formulas involving transition metals and polyatomic ions for a deeper understanding.

Transcripts

Let's talk about how to write chemical formulas for ionic compounds.

So what this means is we're going to start the chemical name like Magnesium Chloride

and learn the steps that we have to go through to take this chemical name and use it to write

a chemical formula like MgCl2, okay?

Let's start with the first example, Lithium Oxide.

So when I'm doing these kind of problems, the first thing that I want to do is find

both these elements on the periodic table.

I'm using this kind of weird version of the periodic table that I just wrote out.

I left out a lot of the elements because they're not important for what we're doing here and

I thought that they're kind of distracting but don't be confused.

This really is no different from periodic table you probably have in your book, it's

just that it's missing a lot of the elements.

Anyway, Lithium . . . where do I find that?

It's right here, Li, and Oxide.

Oxide is just another word for Oxygen, it's what we call Oxygen when Oxygen has a charge

and I'm going to talk a little bit more about that later.

Anyway, Oxide is just another word for Oxygen and Oxygen is over here.

They're on opposite sides of the periodic table and check this out too.

There's this big thick staircase that separates Lithium from Oxygen.

What's a staircase doing?

If you remember, the staircase separates the metals on this side of the periodic table

from the nonmetals on this side of the periodic table.

So Lithium's a metal and Oxygen is a nonmetal.

This is important because we have a metal and a nonmetal connected together and that

means that we're dealing with an ionic compound.

Ionic compounds are always metals and nonmetals.

So we have metals and nonmetals making an ionic compound, that means that the atoms

in that compound have a charge, so I want to find out what the charge of those atoms

is and I can do that by looking at where they live, what column they live in on the periodic

table.

Here's what I mean.

So Lithium lives within this column.

Everything in this column has a plus one charge, so I'm going to write this right here . . . Li+1

. . . everything in this column has a two plus charge (+2), three plus charge (+3),

you may want to write this on your own periodic table that you have for your reference.

Everything here has a 3 minus charge (-3) and Oxygen which lives in this column has

a two minus charge (-2) so I'm going to write it right here.

So Li+1, O2-.

Okay, so now I ask myself, does the plus charge (+) and the minus charge (-) balance when

I have one atom of both of these?

The answer is no because I have one plus charge but I have two minus charges so the charges

don't balance.

But I want to figure out how to balance them.

I need to have them balanced in order to write the chemical formula, so what I can do is

I can add more Lithium atoms, I can add more Oxygen atoms, or I can add both of them until

I get the charges to balance out.

I have two minus (2-) here and only one plus (+1) here so what I'm going to do is I'm going

to add another Lithium atom, Li+, so that now I have two positive to balance out my

two negative and now they balance.

So in order to get the charges balanced, I have to have two Lithiums and one Oxide or

one Oxygen.

Now when I write the chemical formula, I'm literally going to say how many of each of

these atoms I need in order for the charges to balance.

We've said that it's two Lithium atoms so I'm going to write "Li" and then the two after

it that indicates that I have two lithium atoms and then one "O" to show that I have

one Oxygen and I'm not going to write anything after that.

If you have a letter without anything after it, it means that you just have one of them.

So Lithium Oxide, two Lithiums and one oxygen, is how we get the charges to balance for this

compound.

Here's the next one, Potassium Nitride.

Just as before, I'm going to take out the periodic table and I'm going to find both

of these guys on it.

Potassium is K, it's right over here and Nitride is what we call Nitrogen when it has a charge

on it and so Nitrogen is over here.

Check it out!

Metal, non-metal, separated by this big thick staircase and so we know we're dealing with

an ionic compound and whenever we think about ionic compound . . . metals and nonmetals

. . . we want to think charges, what charges does the atoms have?

Potassium lives in this column here, the same column as Lithium and so it has a one plus

charge (+1) so I'm going to write that up here, K+.

And Nitrogen lives in this column where everything has a minus three charge (-3) so here we have

N3-.

When I have one atom of K+ and one atom of N3- do the charges balance out here?

Doe the plus and minus balance out?

It doesn't, I got one plus and I've got three minus, that doesn't balance right.

But I could add more atoms of either type in order to get the charges to balance.

So since I don't have as much pluses as I have minuses I'm going to add a bunch of more

Potassium.

Here I add another, now I have 2+, and now I'm going to add one more and I have 3+ . . . 3+

Potassium on this side balances out the 3- Nitride on this side.

Now when I write my chemical formula, I want to literally say how many atoms of each type

I need for the charges to balance.

I'm going to need three Potassiums so I'm going to write "K3" and I only need one nitrogen

or one Nitride so I'm going to write "N" with nothing after it and if I don't write anything

after, it means one.

So three Potassiums, one Nitrogen, the correct formula for this is K3N.

Okay, here's another one.

Sodium Chloride which is the name of common table salt.

Once again, I'm going to find them both on the periodic table.

Sodium right here is in the one plus (+1) column and Chlorine or Chloride is in this

column right here.

We've got metal and nonmetal so we're dealing with ionic compounds which means the atoms

have charges.

Now I want to figure out what the charges are.

As I said before, Na is in the one plus (+1) so an atom of Sodium has a one plus (+1) charge

here and then Chloride is what we call Chlorine when it has a charge and Chlorine lives in

this column so it has a one minus charge (-1) so Cl-.

Okay, so I have one atom of Sodium plus one (Na+) and I have one atom of Chloride minus

one (Cl-).

When I have an atom of both of these, does the positive and negative balance out?

It does, I don't need to add more of either one of these atoms, I'm totally set.

So to write the chemical formula for Sodium Chloride I want to say again how many of each

I need for the charges to balance out.

I'm just going to say NaCl.

I don't put any numbers after them because if I don't put a number it means I just have

one.

So I have one Sodium and one Chloride, okay?

You might be getting the hang of this.

I want to try to convince you to watch this one last example because it's a tricky one

that confuses a lot of people.

Aluminum Oxide.

Once again, periodic table.

Aluminum here, Oxygen here, metal, non-metal, it's ionic which means charges are important.

So Aluminum is in the three plus (+3) column, one atom or ion of Aluminum, an ion is what

we call an atom that has a charge.

An ion of Aluminum has a three plus charge (+3) and an atom of Oxygen or oxide here has

a two minus charge (-2), Al2+ O2-.Now I need to figure out how many of each of these atoms

I need for the charges to balance out and this example is a little bit trickier than

the ones before.

How are we going to be able to add atoms to get the same number of positive and negative

charge?

Let me give you a hint.

We're going to start by adding another Aluminum atom in here or Aluminum ion to be precise.

So now I have three plus here and three-plus here, each Aluminum atom has a charge of three

plus (+3) so I have a total of six plus (+6).

Now I can balance out the six plus by adding more of the Oxygen.

I add one more Oxygen and I have a total of four minus and I add one more I have a total

of six minus.

So this is how we balance out the charges in Aluminum Oxide with two Aluminum ions with

three plus (+3) each, total of six plus (+6), and three Oxygen ions with a total of two

minus (-2) each which gives us minus six (-6).

Now I'm going to write the chemical formula to show how many each I need to have.

That's going to be Al2 and O3.

I have two Aluminums and three Oxygens.

Okay, so now let me tell you what I'm going to do.

If you're still a little bit shaky on this, I'm going to do a few more practice problems

in a minute.

If you feel really good about this, you might want to just turn the video off and go and

watch videos I have on writing formulas for compounds with transition metals and for compounds

with polyatomic ions.

But before I do a few more practice problems I want to talk about two commonly made mistakes

so many people make when they're writing these formulas so you might just want to stick around

to watch that.

Here are the two mistakes people make.

Let's assume that you're asked to write the chemical formula for Lithium Oxide, you do

this you find out you want to have two Lithiums with one plus each to balance out the charge

on Oxygen, okay?

Here is one mistake that people make.

They say, okay, I have two Lithiums and one Oxygen so I'll write LiO1.

They say yeah, yeah, yeah there's only one Oxygen so it can't hurt to just add the O1

here, can it?

It can't hurt.

It does hurt!

It's just not right to do, you never want to put a one after an element.

So Li2O1 is wrong.

Instead, you want to write Li2O without any numbers after this and this is the right way

to do it.

Here's another mistake that people often do.

They don't remember to get rid of the charges when they write the chemical formula.

So they end up writing something like Li+2O2- where the charges that were on the atoms here

stay when they write the chemical formula.

This also unfortunately is wrong.

When you write the chemical formula you want to get rid of all of the charges so you just

write again Li2O.

Make sure there aren't any charges in the chemical formula when you finally right it,

okay?