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

S^2- sulfide ion

O^2- 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^- = NaNO_{2 -} 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

IO_{3 -} iodate

-2 oxidation number

S₂O₃^-2 - Thiosulfate

SO₃²⁻ sulfite

SO₄²⁻ sulfate

CO₃²⁻ carbonate

PO₄³⁻ phosphate

HPO₄²⁻ hydrogen phosphate

CrO₄²⁻ chromate

Cr₂O₇²⁻ dichromate

C₂O₄²⁻ oxalate

O₂^2- peroxide

-3 oxidation number

BO₃³⁻ orthoborate

AsO₄³⁻ arsenate

PO₄^3-

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 (S^2-) 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 (SO₄^2-) 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 (PO₃^3-) 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.

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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

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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

SO₄^2- Sulfate ion

CO₃^2- Carbonate ion

PO₄^3- 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

SO₃^2- Sulfite ion

PO₃^3- 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^- -PbCl_{2 -} 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