How to Name Compounds with Polyatomic Ions


pink water moleculesAim: How to Name compounds with polyatomic ions.

Materials: Index Cards, markers

Background information: REVIEW: (These compounds to follow ARE NOT binary compounds. They contain three or more elements, as opposed to only two in a binary compound. Don’t use the Greek method. That naming technique is used only for binary compounds of two nonmetals. That means, if you see a formula like BaSO4, the name is not barium monosulfur tetraoxide. Many unaware students over the years have made this error and suffered for it.)

Goals: students should be able to learn to recognize the presence of a polyatomic ion in a formula.

Activity:

students will make a set of flashcards with the name on one side and the ion and its charge on the other. Then, carry them everywhere and use them. The cations used will be a mix of fixed charges AND variable charges. You must know which are which.

Students will associate the charges with each polyatomic ion. For example, NO3¯ is called nitrate and it has a minus one charge.

Notes: glencoe chemistry,  zumdahl & zumdahl

1. When more than one polyatomic ion is required, parenthesis are used to enclose the ion with the subscript going outside the parenthesis. For example, the very first formula used is Fe(NO3)2. This means that two NO3¯ are involved in the compound. Without the parenthesis, the formula would be FeNO32, a far cry from the correct formula.

2. How to say a formula. When you speak a formula involving parenthesis out loud, you use the word “taken” as in the formula for ammonium sulfide, which is (NH4)2S. Out loud, you say “N H four taken twice S.” OR with the formula for copper(II) chlorate, which is Cu(ClO3)2. You say ” Cu Cl O three taken twice.”


Example #1 – write the name for Fe(NO3)2

Step #1 – decide if the cation is one showing variable charge. If so, a Roman numeral will be needed. In this case, iron does show variable charge.

If a variable charge cation is involved, you must determine the Roman numeral involved. You do this by computing the total charge contributed by the polyatomic ion. In this case, NO3¯ has a minus one charge and there are two of them, making a total of minus 2.

Therefore, the iron must be a positive two, in order to keep the total charge of the formula at zero.

Step #2 – determine the name of the polyatomic ion. Nitrate is the name of NO3¯.

The correct name is iron(II) nitrate. The common name would be ferrous nitrate.


Example #2 – write the name for NaOH

Step #1 – the cation, Na+, does not show a variable charge, so no Roman numeral is needed. The name is sodium.

Step#2 – OH¯ is recognized as the hydroxide ion.

The name of this compound is sodium hydroxide.


 

There are three things you must memorize: the name (hydroxide), the symbol (OH) and the charge (minus one).


Example #3 – write the name for KMnO4

Step #1 – the cation, K+, does not show a variable charge, so no Roman numeral is needed. The name is potassium.

Step#2 – MnO4¯ is recognized as the permanganate ion.

The name of this compound is potassium permanganate.


Example #4 – write the name for Cu2SO4

Step #1 – decide if the cation is one showing variable charge. If so, a Roman numeral will be needed. In this case, copper does show variable charge.

If a variable charge cation is involved, you must determine the Roman numeral involved. You do this by computing the total charge contributed by the polyatomic ion. In this case, SO42¯ has a minus two charge and there is only one, making a total of minus 2.

Therefore, the copper must be a positive one. Why? Well, there must be a positive two to go with the negative two in order to make zero. Since the formula shows two copper atoms involved, each must be a plus one charge.

Step #2 – determine the name of the polyatomic ion. Sulfate is the name of SO42¯.

The correct name is copper(I) sulfate. The common name would be cuprous sulfate.


Example #5 – write the name for Ca(ClO3)2

The first part of the name comes from the first element’s name: calcium. You also determine that it is not a cation of variable charge.

The second part of the name comes from the name of the polyatomic ion: chlorate.

This compound is named calcium chlorate.


Example #6 – write the name for Fe(OH)3

Iron is an element with two possible oxidation states. The iron is a +3 charge because (1) there are three hydroxides, (2) hydroxide is a minus one charge, (3) this gives a total charge of negative three and (40 there is only one iron, so it must be a +3.

Therefore the first part of the name is iron(III).

The second part of the name is hydroxide, the name of the polyatomic ion.

The name of this compound is iron(III) hydroxide (or ferric hydroxide when using the common method).


 Home work:

The cations in this first set are all of fixed oxidation state, so no Roman numerals are needed.

Write the correct name for:

1) AlPO4

2) KNO2

3) NaHCO3

4) CaCO3

5) Mg(OH)2

6) Na2CrO4

7) Ba(CN)2

8) K2SO4

9) NaH2PO4

10) NH4NO3

 

These formulas involve the use of a polyatomic ion. The cations are all of variable oxidation state, so Roman numerals are needed.

Write the correct name for:

11) Sn(NO3)2

12) FePO4

13) Cu2SO4

14) Ni(C2H3O2)2

15) HgCO3

16) Pb(OH)4

17) Cu2Cr2O7

18) Cu(ClO3)2

19) FeSO4

20) Hg2(ClO4)2

 

These formulas mix the use of the two types of cations.

Write the correct name for:

21) KClO3

22) SnSO4

23) Al(MnO4)3

24) Pb(NO3)2

25) Mg3(PO4)2

26) CuH2PO4

27) CaHPO4

28) Fe(HCO3)3

29) Na2CO3

30) MnSO4

Homework: handout completion of chemical formulas  or (p224 #19-23) ion pairs

Relating Work to Power


Aim: 

How work, energy, and power are interelated.

How to use formulas to solve problems related to work, energy, and power.

1.       State the law of conservation of energy.   Why does a swinging pendulum eventually come to rest if this law is true? (ie, where does the energy go?)

The law of conservation of energy states that energy can be neither created nor destroyed.   A pendulum will eventually slow and stop because of the downward pull of gravity and air resistance.   The energy lost by the pendulum, however, is gained by the air molecules that are displaced by the pendulum.

2.      Describe the two conditions necessary for work to be done on an object.

Work is done when a force is applied to an object and that object moves in the same direction as the applied force

3.      What is the relationship between work and energy?

Work and energy are related in that there is a transfer of energy from the object applying a force to the object that moves as a result of that force.

4.     A 1000-newton force is applied to a stalled car, causing it to move 8 meters.   How much work is done on the car?

Work   =   force   x   distance

 

W   =   1000 N   x   8 m

 

            W   = 8000 Joules

5.      Two students, each weighing 500 newtons, must travel   700 meters to get from the parking lot to their first period class.   Student A walks and gets to his destination in 200 seconds.   Student B runs and gets there in 100 seconds.

a.      Which student does more work?   Support your answer with calculations

Both students do the same amount of work because their mass is the same and their distance to class is the same…

Work   =   force   x   distance

W   =   500 N   x   700 meters

W   =   350,000 Joules

b.      Which student has more power?   Support your answer with calculations.

Student B has more power because they did the same amount of work in half the time as student A.

Student A                                                                         Student B

            Power   =   work/time                                                             Power   =   work/time

            P   =   350,000 J/100 seconds                                                 P   =   350,000 J/200 seconds

            P   =   35,000 watts                                                    P   =   17,000 watts
Homeworkp 835 #40-55

How to Name Binary Molecular Compounds


Aim: How to name binary molecular compounds, when 2 nonmetals are involved.

Notes: glencoe science assessment

1. A binary compound is one made of two different elements. There can
be one of each element such as in CO or NO. There can also be several
of each element such as BF or OCl2.

2. In this type of compound there are no cations! 

3. You dont have to know the charges. Just use the element names and their prefixes. Be aware that
heavy use of Greek number prefixes are used in this lesson.Here are the
first ten:

		one	mono-			six	hexa-
two di- seven hepta-
three tri- eight octa-
four tetra- nine nona-
five penta- ten deca-

Example #1 – write the name for N2O.

Example #2 – write the name for NO2.

Step #1 – part of the first name is the unchanged name of the first
element in the formula. In the examples above, it would be nitrogen.

If the subscript of the first element is 2 or more, you add a prefix
to the name. In the first example above, you would write dinitrogen. If
the subscript is one as in the second example above, you DO NOT use a prefix. You simply write the name, in this example it would be nitrogen.

Step #2 – the anion is named in the usual manner of stem plus “ide.”
In addition, a prefix is added. In the first example, the prefix is
“mono-” since there is one oxygen. In the second example, use “di-”
because of two oxygens.

The correct names of the two examples are dinitrogen monoxide and nitrogen dioxide.

Note that “monoxide” is written rather than “monooxide.” It sounds better when spoken out loud.


Example #3 – write the name for IF7.

Step #1 – the first element is iodine and there is only one. This part of the name will be “iodine”, NOT “monoiodine.”

Step #2 – the second element is fluorine, so “fluoride” is used. Since there are seven, the prefix “hepta” is used.

The name of this compound is iodine heptafluoride.


Example #4 – write the name for N2O5.

Step #1 – the first element is nitrogen and there are two. This part of the name will be “dinitrogen.”

Step #2 – the second element is oxygen, so “oxide” is used. Since there are five, the prefix “penta” is used.

The name of this compound is “dinitrogen pentaoxide.” Many write is
as “dinitrogen pentoxide.” The ChemTeam believes that both are
considered correct, but the second is to be prefered.


Example #5 – write the name for XeF2.

The first part of the name comes from the first element’s name: xenon. Since there is only one atom present, no prefix is used.

The second part of the name comes from the root of the second symbol
plus ‘ide’ as well as the prefix “di-,”therefore di + fluor + ide =
difluoride.

This compound is named xenon difluoride.


Example #6 – write the name for N2O4.

The first part of the name comes from the first element’s name:
nitrogen. Since there are two atoms, the prefix “di-” is used giving
dinitrogen.

The second part of the name comes from the root of the second symbol
plus ‘ide’ as well as the prefix “tetra-,”therefore tetr + ox + ide =
tetroxide.

This compound is named dinitrogen tetroxide. Notice the dropping of the “a” in tetra.


Just a reminder: this system of naming does not really have an
offically accepted name, but is often called the Greek system (or
method). It involves use of Greek prefixes when naming binary compounds
of two nonmetals.

Sometimes you will see the Stock system applied to these types of
compounds. Here is what the IUPAC currently says about that practice:
“The Stock notation can be applied to both cations and anions, but
preferably should not be applied to compounds between nonmetals.”


Acitivity
Write the correct name for:

1) As4O10

2) BrO3

3) BN

4) N2O3

5) NI3

6) SF6

7) XeF4

8) PCl3

9) CO

10) PCl5


Write the correct name for:

11) P2O5

12) S2Cl2

13) ICl2

14) SO2

15) P4O10

16) UF6

17) OF2

18) ClO2

19) SiO2

20) BF3


Write the correct name for:

21) N2S5

22) CO2

23) SO3

24) XeF6

25) KrF2

26) BrCl5

27) SCl4

28) PF3

29) XeO3

30) OsO4