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Friday, August 14, 2009

Guided lecture on the Nomenclature on Inorganic Chemistry

Nomenclature Inorganic Compounds

By. Eduardo D, Danda II, RMT

Important: before you study this, make it sure that you have some basic understanding on the table of elements like the symbol and thier corresponding name, family it belong whether metal, metalloid, non-metal or the group being classified such as group I,II, III and so forth. Be reminded that there elements have 2 oxidation numbers while some have only one.

This lecture is not complete as you expect, that's why your descretion is advice. This is just guide lecture as you study chemistry one.

Here are some of the hints:

Monoatomic ions ( indicate their name opposite to the symbol)

Cations

+1 charge +2 charges +3 charges

Cs Ba+2 Al +3

Cu Cd+2 Cr+3

Li Cd+2 Fe+3

K Cr+2

Pb Co+2

Ag Fe+2

Na Pb+2

Mg+2

Mn+2

Hg+2

Ni+2

Anions

-1 charge -2 charges -3 charges

Br- O-2 N-3

Cl- S-2

F-

I-

Note 1: for element with +1/-1 charge – no need to write the number

Note 1: Most of the cations are the non-metal ( found at the left part of the table)

Ionic compounds: (an association of a cation and an anion)

The positive ion (cation) is always named first and listed first in writing the formula for the compound.

The vast majority of monatomic (composed of a single atom) cations are formed from metallic elements:

Na+ Sodium ion

Zn2+ Zinc ion

Al3+ Aluminum ion


If an element can form more than one positive ion, the positive charge of the ion is indicated by a Roman numeral in parentheses following the name of the metal:

  • Fe2+ iron(II) ion
  • Fe3+ iron(III) ion
  • Cu+ copper(I) ion
  • Cu2+ copper(II) ion

Iron and copper are examples of transition metals. They occur in the block of elements from IIIB to IIB of the periodic table.

The transition metals often form two or more different monoatomic cations.

An older nomenclature for distinguishing between the different ions of a metal is to use the suffixes -ous and -ic. The suffix -ic will indicate the ion of higher ionic charge:

  • Fe2+ ferrous ion
  • Fe3+ ferric ion
  • Cu+ cuprous ion
  • Cu2+ cupric ion

Note that the different ions of the same element often have quite different chemical properties (again, pointing to the importance of electrons in determining chemical reactivity).

Ionic compounds: Anions

Monatomic anions are usually formed from non-metallic elements. They are named by dropping the ending of the element name and adding -ide:

Cl- chloride ion

F- flouride ion

S2- sulfide ion

O2- oxide ion

Cl chloride

S2− sulfide

P3− phosphide

Some common polyatomic anions include:

  • OH- hydroxide ion
  • CN- cyanide ion

Many polyatomic anions contain oxygen, and are referred to as oxyanions. When an element can form two different oxyanions the name of the one that contains more oxygen ends in -ate, the one with less ends in -ite:

+ 1

NH4+ ammonium

H3O+ hydr-oxonium

-1 oxidation number

NO2- nitrite ion ex Na+ + NO2- = NaNO2 - Sodium Nitrite

NO3- nitrate ion

ClO hypochlorite

ClO2 chlorite

ClO3 chlorate

ClO4 perchlorate

CN cyanide

SCN thiocyanate

MnO4 permanganate

HSO3 hydrogen sulfite (or bisulfite) ex. K+ + HSO3- - KHSO3 = Potasium bisulfite

H2PO4 dihydrogen phosphate

HCO3 hydrogen carbonate (or bicarbonate)

IO - hypoiodite ion

IO3 - iodate

-2 oxidation number

S2O3-2 - Thiosulfate

SO32− sulfite

SO42− sulfate

CO32− carbonate

PO43− phosphate

HPO42− hydrogen phosphate

CrO42− chromate

Cr2O72− dichromate

C2O42− oxalate

O22- peroxide

-3 oxidation number

BO33− orthoborate

AsO43− arsenate

PO43-

Note that unlike the -ous and -ic suffix nomenclature to distinguish the different cations of a metal, the -ite and -ate suffix is used to distinguish the relative amounts of the oxygen atoms in a (polyatomic) oxyanion (in the above examples the ionic charge is the same for the -ite and -ate ions of a specific oxyanion).

Some compounds can have multiple oxyanion forms (the oxyanions involving the halogens, for example):

  • ClO-
  • ClO2-
  • ClO3-
  • ClO4-

Note again, that the number of Oxygens relative to the Chlorine is changing, but that the ionic charge is not.

How do we name these? The -ite and -ate suffixes are still used, but we have to add an additional modification to allow us to distinguish between the four forms:

  • ClO- hypochlorite ion
  • ClO2- chlorite ion
  • ClO3- chlorate ion
  • ClO4- perchlorate ion

BINARY COMPOUNDS OF NITROGEN AND OXYGEN

Binary Molecular Compounds

When a pair of elements form more than one type of covalent compound, Greek prefixes are used to indicate how many of each element are in a compound. The more electronegative element is written last and its ending is changed to –ide.

Examples

N2O dinitrogen monoxide

NO nitrogen monoxide

N2O3 dinitrogen trioxide

N2O5 dinitrogen pentoxide

It should be pointed out that some of the naming of ions is historical and is not necessarily systematic. It may be frustrating and confusing, but its all part of chemistry's rich history.

Many polyatomic anions that have high (negative) charges can add one or more hydrogen cations (H+) to form anions of lower effective charge. The naming of these anions reflects whether the H+ addition involves one or more hydrogen ions:

  • HSO4- hydrogen sulfate ion
  • H2PO4- dihydrogen phosphate ion

Acids

We constantly encounter acids in everyday life, from citric acid and ascorbic acid (vitamin C) to acetic acid (vinegar) and hydrochloric acid. We will consider acids in more detail in the next two chapters, but before we can do that we must be able to name common acids.

A simplistic definition of an acid is a compound that dissolves in water to release H+ ions. The most common acids are those which result when we add enough H+ ions to an oxyanion to balance its charge. The rules for naming simple acids are based on the names of the anions, they are given below.

(1) When the anion ends in -ide, change the ending to -ic and add the prefix hydro- to derive the name of the acid.

  • Anion = chloride (Cl-) hydrochloric acid (HCl)
  • Anion = bromide (Br-) hydrobromic acid (HBr)
  • Anion = sulfide (S2-) hydrosulfuric acid (H2S)

(2) When the anion ends in -ate, change the ending to -ic to derive the name of the acid.

  • Anion = chlorate (ClO3-) chloric acid (HClO3)
  • Anion = sulfate (SO42-) sulfuric acid (H2SO4)
  • Anion = nitrate (NO3-) nitric acid (HNO3)

(3) When the anion ends in -ite, change the ending to -ous to derive the name of the acid.

  • Anion = phosphite (PO33-) Phosphorous acid (H3PO3)
  • Anion = chlorite (ClO2-) Chlorous acid (HClO2)
  • Anion = hypochlorite (ClO-) Hypochlorous acid (HClO)

Naming acids

Acids are named by the anion they form when dissolved in water. If an acid forms an anion named ___ide, it is named hydro___ic acid. For example, hydrochloric acid forms a chloride anion. With sulfur, however, the whole word is kept instead of the root: i.e.: hydrosulfuric acid. Secondly, anions with an -ate suffix are formed when acids with an -ic suffix are dissolved, e.g. chloric acid (HClO3) dissociates into chlorate anions to form salts such as sodium chlorate (NaClO3); anions with an -ite suffix are formed when acids with an -ous suffix are dissolved in water, e.g. chlorous acid (HClO2) disassociates into chlorite anions to form salts such as sodium chlorite (NaClO2).

Memory recall……………..

  • An acid is a substance whose molecules yield hydrogen (H+) ions when dissolved in water.
  • The formula of an acid consists of an anionic group whose charged is balanced by one or more H+ ions.
  • The name of the acid is related to the name of the anion
  • Anions whose names end in -ide have associated acids that have the hydro- prefix and an -ic suffix:

Cl- chloride anion

HCl hydrochloric acid

S2- sulfide anion

H2S hydrosulfuric acid

SO42-

H2SO4 Sulfuric acid

Using the -ic suffix here may seem a bit inconsistent since it was used in naming metal cations to indicate the form which had the higher positive charge. However, when you think about it, the acid compound has a higher net positive charge than the anion from which it is derived (the anion is negatively charge and the associated acid is neutral).

Again, things get complicated when we consider the acids of oxyanions:

  • If the anion has an -ate ending, the corresponding acid is given an -ic ending
  • If the anion has an -ite ending, the corresponding acid has an -ous ending.
  • Prefixes in the name of the anion are kept in naming the acid

ClO- hypochlorite ion

HClO hypochlorous acid

ClO2- chlorite ion

HClO2 chlorous acid

ClO3- chlorate ion

HClO3 chloric acid

ClO4- perchlorate ion

HClO4 perchloric acid

This is confusing: we previously had used the -ous and -ic suffixes to indicate the ionic charge differences in metal cations (-ic had a higher positive charge). Although in comparison to the ionic form, the -ic and -ous acid forms have a higher net positive charge, the -ic suffix would indicate forms with a higher oxygen content, and not an apparent charge difference.

Molecular compounds

Although they may not be ionic compounds, chemically bonded compounds of two different elements can be thought of as being made up of an element with a more positive chemical nature, and one that has a more negative nature in comparison. Elements on the left hand side of the periodic table prefer to donate electrons (thus taking on a more positive chemical nature), and elements on the right hand side prefer to accept electrons (thus taking on a more negative chemical nature). The element with the more positive nature in a compound is named first. The second element is named with an -ide ending.

Often a pair of elements can form several different molecular compounds. For example, Carbon and Oxygen can form CO and CO2. Prefixes are used to identify the relative number of atoms in such compounds:

  • CO carbon monoxide (carbon mono oxide)
  • CO2 carbon dioxide

Such prefixes can extend for quite a way for some organic and polymeric compounds (a common detergent in shampoos is sodium dodecylsulfate, or "SDS", also known as Sodium Laurel Sulfate because it sounds more benign and holistic). The list of such prefixes includes:

Prefix

Meaning

Mono-

1

Di-

2

Tri-

3

Tetra-

4

Penta-

5

Hexa-

6

Hepta-

7

Octa-

8

Nona-

9

Deca-

10

Undeca-

11

Dodeca-

12

MEMORY RECALL……………..

How do you know which element goes first?

(A) The element that comes first in the following list "goes" first (is less electronegative).

B, Si, C, Sb, As, P, N, H, Te, Se, S, I, Br, Cl, O, F

Some additional rules

  • The prefix mono is never used for naming the first element of a compound.
  • The final "o" or "a" of a prefix is often dropped when the element begins with a vowel.

Examples

  • CO carbon monoxide
  • ClO2 chlorine dioxide

Finally, H2O, which according to the rules should be called dihydrogen monoxide is always called water, and NH3, or nitrogen trihydride, is always called ammonia.


Ionic compounds

Let’s review some of the features of ionic compounds

  • Metals give up electrons to form positively charged cations.
  • Non-metals gain electrons to form negatively charged anions.
  • Ionic compounds are formed from the Coulombic interaction between cations and anions.

NAMING AND WRITING ORGANIC COMPOUND

When we name an ionic compound, we write

(1) The name of the cation comes first followed by the name of the anion, changing the name of the anion to end in –ide for monotomic anions. The names of polyatomic anions are not altered.

Examples

  • NaCl sodium chloride
  • ZnI2 zinc iodide
  • NaNO3 sodium nitrate
  • Ag2CO3 silver cabonate
  • (NH4)2SO4 ammonium sulfate

(2) In those cases where the metal can form cations of differing charges the positive charge is given by a roman numeral in parentheses

  • CuO copper (II) oxide
  • Cu2O copper (I) oxide
  • Cr2O3 chromium (III) oxide

Ionic compounds

Let’s review some of the features of ionic compounds

  • Metals give up electrons to form positively charged cations.
  • Non-metals gain electrons to form negatively charged anions.
  • Ionic compounds are formed from the Coulombic interaction between cations and anions.

When we name an ionic compound, we write

(1) The name of the cation comes first followed by the name of the anion, changing the name of the anion to end in –ide for monotomic anions. The names of polyatomic anions are not altered.

Examples

NaCl sodium chloride

ZnI2 zinc iodide

NaNO3 sodium nitrate

Ag2CO3 silver cabonate

(NH4)2SO4 ammonium sulfate

(2) In those cases where the metal can form cations of differing charges the positive charge is given by a roman numeral in parentheses

CuO copper (II) oxide

Cu2O copper (I) oxide

Cr2O3 chromium (III) oxide

Oxyanions

Oxyanions are those polyatomic anions containing oxygen. There are a large number of oxyanions, which makes it difficult to remember all of their names. Fortunately there is a set of rules that makes this task much easier. The rules for naming oxyanions and the names for the most important oxyanions are given below.

(1) The ending -ate is used for the most common oxyanion of a given element.

NO3- Nitrate ion

SO42- Sulfate ion

CO32- Carbonate ion

PO43- Phosphate ion

ClO3- Chlorate ion

(2) The ending -ite is used for the oxyanion with the same charge, but one less oxygen than the -ate oxyanion.

NO2- Nitrite ion

SO32- Sulfite ion

PO33- Phosphite ion

ClO2- Chlorite ion

(3) The prefix per- is used if there is an oxyanion with the same charge but one more oxygen than the -ate oxyanion, while the prefix hypo- is used if there is an oxyanion with the same charge but one less oxygen than the -ite oxyanion.

ClO4- percholorate ion

ClO3- chlorate ion

ClO2- chlorite ion

ClO- hypochlorite ion


Memory Check ……………….

The exact chemical compound and its corresponding name:

Cu+2 + I- - CuI2 - Copper (II) iodide

Fe+2 + O- -FeO - Iron (II) oxide

Pb+2 + Cl- -PbCl2 - Lead (II) chloride

Hg+2 + S- _____ _________________

Sn+2 + F- _____ _________________

CuO _________________

Snl4 _________________

FeS _________________

Hg2Cl2 _________________

Note in this chemical reaction, this involve an ions that has two possible oxidation number. In old way of naming , if the oxidation number is LOWER it ends with OUS while those with higher oxidation number it ends with _IC

Cu (I) - cupprous

(II) – Cupric

Fe (II) - Ferrous

(III) - Ferric

Pb (I) -Plumbous

(II) - Plumbic

Hg (I) - Mercurous

- Mercuric

Ar ____ _________

____ _________

Mn ____ _________

____ _________

Au Aurous

Auric

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