Chemistry Lesson: Naming Ionic Compounds
Summary
TLDRIn 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
🔬 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.
🧪 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.
🧮 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.
Mindmap
Keywords
💡Ionic Compounds
💡Cation
💡Anion
💡Fixed Charge Metals
💡Variable Charge Metals
💡Roman Numerals
💡Monoatomic Ions
💡Polyatomic Ions
💡Charge Balance
💡Magic Triangle
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
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