Chemistry Lesson: Naming Ionic Compounds

Summary

In this lesson from GetChemistryHelp.com, Dr. Kent continues the series on ionic compounds by teaching how to name compounds from their chemical formulas. He explains the difference between fixed charge metals (Type 1) and variable charge metals (Type 2) and demonstrates how to determine the charge of a metal based on the anion in the compound. Using several examples like cobalt nitride, mercury sulfide, and iron nitrate, Dr. Kent shows how to balance the charges and apply the correct nomenclature, providing a deeper understanding of naming ionic compounds.

Takeaways

• 🔢 Ionic compounds generally have metals as the cation, but polyatomic ions like ammonium can also serve as the cation.
• ⚖️ Metals can have fixed or variable charges; fixed-charge metals are called type 1, and variable-charge metals are called type 2.
• 📜 Fixed-charge metals are usually found in groups 1, 2, and a 'Magic Triangle,' including elements like lithium, sodium, and magnesium.
• 🔄 Variable-charge metals (e.g., iron, tin) require a Roman numeral in their names to indicate the specific charge (e.g., Iron(II) or Iron(III)).
• ⚛️ Non-metals gain electrons to match the nearest noble gas configuration, and their names are changed by adding the '-ide' suffix, like nitride or sulfide.
• 🧪 For variable-charge metals, the charge is determined based on the corresponding anion’s charge to balance out the ionic compound.
• ⚗️ Polyatomic ions like nitrate (NO3⁻) and cyanide (CN⁻) must be memorized, as their names don't follow simple naming rules.
• ⚙️ Compounds with fixed-charge metals (e.g., magnesium fluoride) don't need Roman numerals because their charge doesn't vary.
• 🧮 Naming ionic compounds involves balancing the total positive and negative charges, ensuring the formula is neutral overall.
• 🔍 The script covers various examples, demonstrating how to name compounds like mercury(II) sulfide, iron(III) nitrate, and copper(I) oxide.

Q & A

What are ionic compounds typically composed of?

Ionic compounds typically have a metal as the cation. Although 99% of the time it's a metal, they can also have a polyatomic ion like ammonium as the cation.

What is the difference between fixed charge metals and variable charge metals?

Fixed charge metals, also known as Type 1 metals, always have the same charge (e.g., group 1 metals like sodium always have a 1+ charge). Variable charge metals, or Type 2 metals, have charges that can vary (e.g., iron can be 2+ or 3+).

Which metals always have a fixed charge?

Metals in group 1 (e.g., lithium, sodium) always have a 1+ charge, metals in group 2 (e.g., magnesium, calcium) always have a 2+ charge, and metals in the 'Magic Triangle' (aluminum, zinc, and silver) also have fixed charges (aluminum 3+, zinc 2+, silver 1+).

How do we determine the charge of a variable charge metal in a compound?

The charge of a variable charge metal is determined by balancing it with the charge of the anion. For example, if the anion has a 3- charge, the cation must balance it by having an equivalent positive charge.

How is the charge of non-metals determined when they form anions?

Non-metals gain electrons until they reach the electron configuration of noble gases. Non-metals in group 17 gain one electron and have a 1- charge, those in group 16 gain two electrons and have a 2- charge, and those in group 15 gain three electrons and have a 3- charge.

How do we name a compound if the metal has a variable charge?

For variable charge metals, the Roman numeral system is used to indicate the metal's charge in the compound. For example, iron (Fe2+) is named iron(II), and iron (Fe3+) is named iron(III).

What is the naming convention for non-metal anions?

Non-metal anions have their endings changed to '-ide'. For example, when nitrogen becomes an anion, it's named nitride, and when sulfur becomes an anion, it's named sulfide.

How is the charge of an ion in a polyatomic ion determined?

The charge of polyatomic ions must be learned or memorized. For instance, nitrate (NO3) has a 1- charge, while sulfate (SO4) has a 2- charge. These charges are essential for balancing ionic compounds.

How do we name compounds with polyatomic ions?

Compounds with polyatomic ions are named by combining the metal cation's name (with Roman numerals if needed) and the polyatomic ion's name. For example, Fe(NO3)3 is named iron(III) nitrate.

What is the 'Magic Triangle' mentioned in the lesson?

The 'Magic Triangle' refers to three metals that always have fixed charges: aluminum (3+), zinc (2+), and silver (1+). These metals are an exception among transition metals, which typically have variable charges.

Outlines

00:00

🔬 Introduction to Ionic Compound Naming

Dr. Kent welcomes viewers back to the series on ionic compounds. He briefly recaps the previous lessons on naming monoatomic and polyatomic ions, as well as converting names into formulas. This lesson focuses on converting formulas back into names, with a reminder that ionic compounds typically have a metal as the cation, though ammonium can also be a cation in some cases. Dr. Kent explains the difference between fixed charge metals (Type 1) and variable charge metals (Type 2), emphasizing their predictable charges based on group numbers and position in the periodic table.

05:01

🧪 Variable Charge Metals and Ionic Balancing

Dr. Kent dives deeper into how to name ionic compounds when dealing with metals that have variable charges, like iron and cobalt. Using the example of cobalt and nitrogen, he explains how to determine the metal's charge by balancing the overall charge of the compound based on the anion's charge. This process involves ensuring that the total positive charge of the cation equals the total negative charge of the anion, which helps identify the proper Roman numeral for the metal. Several examples, including iron, mercury, and copper, are used to illustrate how the Roman numeral reflects the metal's specific charge in each case.

10:05

🧮 Applying the Rules with Examples

This section continues the lesson with more examples of ionic compounds and their names. For each example, Dr. Kent identifies the metal, checks if it has a fixed or variable charge, and then uses the anion's charge to determine the proper Roman numeral for the metal. The discussion includes compounds like mercury sulfide, iron nitrate, magnesium fluoride, and tin cyanide. The importance of knowing polyatomic ions like cyanide and nitrate is emphasized, as these help in correctly naming the compound. Dr. Kent also notes how some metals, like magnesium, do not require Roman numerals since their charges are always fixed.

Keywords

💡Ionic Compounds

Ionic compounds are chemical compounds formed by the electrostatic attraction between oppositely charged ions. In the video, these compounds are explained as typically consisting of a metal cation and a non-metal anion. The lesson focuses on how to name these compounds and understand their formulas.

💡Cation

A cation is a positively charged ion, usually a metal, in an ionic compound. The video explains that cations are crucial in the formation of ionic compounds, where metals such as those in Group 1 and 2 of the periodic table form fixed charges, while others may have variable charges.

💡Anion

An anion is a negatively charged ion, typically a non-metal, in an ionic compound. The video explains that anions are formed when non-metals gain electrons, and their charge helps determine the charge of the cation in variable charge metals.

💡Fixed Charge Metals

Fixed charge metals are metals whose ionic charge is constant, such as those in Group 1 and Group 2 of the periodic table. The video emphasizes that these metals have predictable charges (e.g., sodium is always +1, magnesium is always +2), simplifying the naming of their compounds.

💡Variable Charge Metals

Variable charge metals can have different ionic charges depending on the compound they form. The video discusses metals like iron, which can exist as either Fe²⁺ or Fe³⁺, and how this variability requires the use of Roman numerals in their names (e.g., Iron (II) or Iron (III)).

💡Roman Numerals

Roman numerals are used in the names of ionic compounds to indicate the charge of a metal with variable charges. In the video, Roman numerals are applied to metals like iron and copper, where their charge must be specified (e.g., Iron (III) for Fe³⁺).

💡Monoatomic Ions

Monoatomic ions are ions consisting of a single atom that has gained or lost electrons. The video mentions that non-metals form monoatomic anions by gaining electrons, such as nitrogen becoming nitride (N³⁻), which is important in naming ionic compounds.

💡Polyatomic Ions

Polyatomic ions are ions composed of two or more atoms covalently bonded, carrying an overall charge. The video discusses polyatomic ions such as nitrate (NO₃⁻) and cyanide (CN⁻), which play a key role in determining the charge balance in ionic compounds.

💡Charge Balance

Charge balance refers to the principle that the total positive charge must equal the total negative charge in an ionic compound. The video illustrates this by showing how the charges of cations and anions combine to form a neutral compound (e.g., Fe³⁺ balancing with NO₃⁻ in iron nitrate).

💡Magic Triangle

The 'Magic Triangle' is a term used in the video to describe a set of metals—aluminum, zinc, and silver—that have predictable, fixed charges (e.g., aluminum is always Al³⁺). This concept simplifies the naming of their compounds because no Roman numerals are needed.

Highlights

Introduction to naming ionic compounds by turning formulas back into names.

Ionic compounds typically have a metal as the cation, though some can have polyatomic ions like ammonium.

There are two types of metals: fixed charge metals (Type 1) and variable charge metals (Type 2).

Fixed charge metals include Group 1, Group 2, and the metals in the 'Magic Triangle'.

Variable charge metals, like iron, require special naming with Roman numerals to indicate their charge (e.g., Iron (II), Iron (III)).

The charge of a variable metal can be determined by balancing it with the charge of the anion.

Example: Cobalt Nitride - Cobalt is a variable charge metal, and Nitride (Nitrogen) has a 3- charge, leading to Cobalt (II) Nitride.

Mercury Sulfide example: Mercury has a variable charge, but Sulfide (Sulfur) has a 2- charge, meaning Mercury must be 2+.

When naming polyatomic ions like Nitrate (NO3-), the metal's charge is calculated based on the number of Nitrate ions.

Magnesium Fluoride example: Magnesium is a fixed-charge metal (2+), so no Roman numeral is needed.

When dealing with cyanides (CN-), as in Tin (IV) Cyanide, the charge is calculated based on the number of cyanide ions.

Copper (I) Oxide example: Oxygen is 2-, and since there are two copper ions, each copper must have a 1+ charge.

Zinc in the 'Magic Triangle' has a fixed charge (2+), meaning no Roman numeral is needed for Zinc Hyposulfite.

For phosphates and phosphites, the charge remains 3-, but the name changes based on the number of oxygen atoms.

Chromium (VI) Phosphite example: Chromium has a 6+ charge balanced by two phosphite ions (3- each).

Transcripts

hello again and welcome to get chemistry

health.com my name is Dr Kent and this

lesson is a continuation of our series

on ionic compounds now in our previous

lessons we learned how to name

monoatomic ions how to name polyatomic

ions and then we learn how to take names

and turn them into formulas well now

we're going to learn how to take

formulas and turn them back into names

so as a quick little

reminder ionic compounds typically have

a metal as the cation now they don't

have to they could have a polyatomic ion

let's say they could have

ammonium could be the Caton but 99% of

the time most of them have a metal now

there's two different types of metals

there are fixed charge metals that means

the charge of those Metals is always the

same those are sometimes called type one

Metals then there are variable charged

metals or what are called type two and

those the charge just like it says can

vary so sometimes they're plus two

sometimes they're three plus so the

fixed ones are easy to pick out those

are all of the metals in group one group

two and then what I call the Magic

Triangle these over here so remember all

of these Metals in group one lithium on

down

here these are all 1 plus so lithium

when it makes an ion makes positive

sodium positive pottassium positive of

Rubidium cesium Etc all of these Metals

in group two on down here well these all

like to be two positive so brillium two

positive magnesium two positive calcium

strontium barium so those are all fixed

charge now the ones over here in the

Triangle these also don't change their

charge so remember I told you in that

lesson that these three aluminum gallium

indium these three like to be three

positive these two zinc and cium like to

be two

positive and this one silver likes to be

one positive so there's three that are

three positive two that are two positive

one that's one positive all of the other

metals pretty much so titanium vadium

mbum I mean just name one tin bismo um

any other one you think of uranium idium

whatever any other metal that's not

group one not in group two not in the

Magic Triangle very likely it's going to

have a variable charge so just for a

little reminder iron iron sometimes it

likes to be Iron 2+ sometimes it likes

to be Iron 3+ and as we said in our

lesson on monoatomic ions since it can

vary we have to name it special so iron

2 plus we call iron 2 with a Roman

numeral iron 3+ we call iron 3 with the

Roman

numeral okay well let's just go through

and and see so if the charge has gone a

vary on the metal well how do we figure

out what it is in a compound well we

figure it out by whatever the charge is

on the annion so for example let's look

at Cobalt three of those and nitrogen

two of those so Cobalt if we peek back

over here Cobalt lives right here so

yeah Cobalt's not in group one it's not

in group two it's not in the Triangle so

it will have a variable charge so I know

it's going to be Cobalt but something

with variable charge I's put parentheses

here well this number is determined by

whatever the charge is on the

anion so let's go back here so here's

nitrogen that's the other part so again

we learned in that lesson on monoatomic

ions that non-metals gain electrons

until they get as many as the noble

gases over here so all of these in group

17 are one away so they all want to be

one negative all of these in group 16

are two away they want to be two

negative all the non-metals in group 15

are threeway they want to be three

negative so nitrogen when it becomes an

annion the ending changes to I we call

it nitride and it gains three electrons

so Cobalt

something

nitride and again nitride is 3 negative

well how many nitrides do we have though

well we got two of them so that's a

total toal of 2 * 3 a total of 6

negative well we learned in ionic

compounds that they always balance out

the positives and the negatives so if

the total negative is 6 negative well

the total positive has to be six

positive okay now six positive though

doesn't mean it's Cobalt six because

there's three Cobalts so the combination

of Cobalts they combine to be six

positive so 3 * what would be six

positive well each one would have to be

two positive so 3 * 2 positive will give

me a total of six positive so must be

Cobalt

2 okay let's just go ahead and work a

few examples here hgs so what's HG HG is

mercury let's find Mercury it lives

right over here okay so it's not in

group one it's not in group two it's not

in our Magic triangle so that means it

does have a variable charge so I know

it's Mercury something why figure out

the charge based off what the anion is

well the annion comes from sulfur so

when sulfur becomes an annion we call it

sulfide non-metals by themselves just go

to ey what would the charge be well it's

one two away from argon so it must be 2

negative right so we got a total of two

negative on the anion so we must have a

total of two positive on the cat I

there's only one so each Mercury must be

two positive Mercury to sulfide great

how about this one let's find Fe so Fe

is iron where does iron live okay right

here so again iron's not in group one

it's not in group

two it's not an our Magic Triangle so

its charge is going to vary so iron

something well we figure out the charge

whatever that is based off the annion so

what's NO3 well as you might recall from

our lesson on polyatomic ions that is

called nitrate

nitrate okay what's the charge on

nitrate well nitrate is one negative but

we have three of them so three one

negatives gives me a total of three

negative so the positive total must be

three positive in order for it to

balance out so there only one iron so it

must be iron 3

nitrate

mgf2 we find

mg okay well mg is in group two so that

means it's always two positive so we

don't need a Roman numeral because it

can only be one

thing so again there's no reason to say

magnesium Roman numeral two because it

can only be two so we just name it

magnesium and then we name F how do we

name that as an anion well it comes from

Florine and when non-metals become

annion they change to I so

magnesium

fluoride and make sure when you spell it

you put the U before the O It's fluoride

not OU fluide

fluide SN parentheses CN parentheses 4

so SN that's called

10 let's find 10 oh number 50

okay well it's not in group one it's not

in group two it's not in our Magic

Triangle so it will need a Roman numeral

we figure it out based off whatever this

is what's CN called well CN is one of

the polyomics you just have to learn

it's called

Cyanide and it has a one negative charge

well we have four cyanides that's a

total of four negative the positives and

the negatives have to balance out so if

that's four negative the 10 must add up

to be four positive there's only one of

them so it must be

104 so 104

cyanide number five

cu2o so CU is

copper so will copper need a Roman

numeral well we got to see where it is

copper is right here so it's definitely

not in group one it's definitely not in

group two and it's not what I like to

call the magic triangle so it's not a

fixed charge so yes it will need a Roman

numeral well we got to figure it out

based off whatever the charge on this is

so oxygen when it becomes a annion the

ending just changes to I so oxide what's

the charge on

oxide well oxygen lives two away so it

would want to gain two electrons to

become at the noble gases so it's 2

negative well we only have one oxygen

that's a total of two negative which

means the the total over here has to be

two positive but notice there's not just

one copper now there's two coppers so

these two coppers combine to give me two

positive so what would each copper have

to be well two * one positive would give

me two positives so each copper must

only be one so copper one

oxide number six zns SO2 so ZN that's

zinc

let's find zinc lives right here so it's

not in group one it's not in group two

oh but it is in our Magic Triangle so

that means its charge doesn't vary

remember these two are always too

positive so I don't need a Roman numeral

but I do need to figure out what this is

so this is a polyatomic sulfur with some

oxygens so we figure out what this is by

knowing what the eight is the one that

ends in eight so what's

sulfate okay well

sulfate is s

so42

Nega so what do we have here well we

have SO2 so this has two less oxygen so

we're down here at s SO2 but still two

negative cuz look we lost two

oxygens so sulfate is so4 what would SO2

be well we change 8 to I

and then we add hypo so it would be

hypo

sulfite zinc

hyposulfite

great number seven CR what's CR well CR

lives right here and that is

chromium so will chromium need a Roman

numeral it sure will it's not in group

one it's not in group two it's not in

our Magic triangle so it charge is going

to vary so we got to give it a Roman

numeral we base it off of whatever this

is so this is a polyatomic in other

words what is the eight for phosphorus

so what is

phosphate well let's see phosphate

hopefully you know is

P4 3 negative what do we have we have

P3 oh well that's one less oxygen right

so instead of phosphate we would call

that

fosite but the charges don't change when

you add or remove oxygen so it's still

three negative okay so phosphite has a

three negative charge how many do we

have we got two phosphites that's a

total of six negative so our catons must

add up to be a total of six positive so

what's chromium have to be there's only

one of them so it must be chromium 6

well hope you enjoyed this lesson on

naming ionic compounds for many more

practice problems be sure and click on

the link and we will see you next time

on getchemistryhelp tocom thank you