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