IUPAC Naming of Salts (Binary Inorganic Ionic Compounds) Introductory Chemistry Tutorial

Key Concepts

Salts are simple inorganic binary ionic compounds.

Salts are composed of two ions (binary means two):
⚛ a cation (positively charged ion)

⚛ an anion (negatively charged ion)

Cations can be composed of
⚛ one atom (monoatomic⁽¹⁾ cation)

⚛ more than one atom (polyatomic cation)

Anions can be composed of
⚛ one atom (monoatomic anion)

⚛ more than one atom (polyatomic anion)

The name⁽²⁾ of a salt is given as two words separate by a space:
⚛ the cation is named first (first word in the salt's name)

⚛ the anion is named last (last word in the salt's name)

Name of Salt

cation name anion name

Name of Salt
cation name		anion name

The table below lists the names of some typical monoatomic cations found in salts:

	Formula of cation	Name of cation	Name of cation used in naming salts
			IUPAC recommended name	alternative names
			IUPAC recommended name	Not recommended⁽³⁾	archaic⁽⁴⁾
	H⁺	hydrogen(1+)	hydrogen
Group 1 (cation charge 1+)	Li⁺	lithium(1+)	lithium
	Na⁺	sodium(1+)	sodium
	K⁺	potassium(1+)	potassium
	Rb⁺	rubidium(1+)	rubidium
	Cs⁺	caesium(1+)	caesium⁽⁵⁾
Group 2 (cation charge 2+)	Mg²⁺	magnesium(2+)	magnesium
	Ca²⁺	calcium(2+)	calcium
	Sr²⁺	strontrium(2+)	strontium
	Ba²⁺	barium(2+)	barium
Group 12 (cation charge 2+)	Zn²⁺	zinc(2+)	zinc
Metals with variable cation charge	Fe²⁺	iron(2+)	iron(2+)	iron(II)	ferrous
	Fe³⁺	iron(3+)	iron(3+)	iron(III)	ferric
	Cu⁺	copper(1+)	copper(1+)	copper(I)	cuprous
	Cu²⁺	copper(2+)	copper(2+)	copper(II)	cupric
	Sn²⁺	tin(2+)	tin(2+)	tin(II)	stannous
	Sn⁴⁺	tin(4+)	tin(4+)	tin(IV)	stannic
	Pb²⁺	lead(2+)	lead(2+)	lead(II)	plumbous
	Pb⁴⁺	lead(4+)	lead(4+)	lead(IV)	plumbic

You may also need to know the formula and name of this polyatomic cation:

Formula of polyatomic cation Systematic IUPAC name Acceptable Non-systematic name

NH₄⁺ azanium ammonium

Formula of polyatomic cation	Systematic IUPAC name	Acceptable Non-systematic name
NH₄⁺	azanium	ammonium

The table lists the formula and acceptable IUPAC names of monoatomic anions you will find in salts:

	Formula	Acceptable IUPAC name ⁽⁶⁾
	H^-	hydride
Group 15 (charge 3-)	N^3-	nitride
Group 15 (charge 3-)	P^3-	phosphide
Group 16 (charge 2-)	O^2-	oxide
Group 16 (charge 2-)	S^2-	sulfide
Group 17 (charge 1-)	F^-	fluoride
	Cl^-	chloride
	Br^-	bromide
	I^-	iodide

You will also need to know the formula and names of some polyatomic anions derived from inorganic acids as shown in the table below:

Inorganic Acid		Polyatomic Anions Derived from Acid
Acceptable Name	Formula	Acceptable Name	Formula
nitric acid	HNO₃	nitrate	NO₃^-
nitrous acid	HNO₂	nitrite	NO₂^-
carbonic acid	H₂CO₃	hydrogencarbonate	HCO₃^-
carbonic acid	H₂CO₃	carbonate	CO₃^2-
sulfuric acid	H₂SO₄	hydrogensulfate	HSO₄^-
sulfuric acid	H₂SO₄	sulfate	SO₄^2-
sulfurous acid	H₂SO₃	hydrogensulfite	HSO₃^-
sulfurous acid	H₂SO₃	sulfite	SO₃^2-
phosphoric acid	H₃PO₄	dihydrogenphosphate	H₂PO₄^-
		hydrogenphosphate	HPO₄^2-
		phosphate	PO₄^3-
phosphorous acid	H₃PO₃	dihydrogenphosphite	H₂PO₃^-
		hydrogenphosphite	HPO₃^2-
		phosphite	PO₃^3-
perchloric acid	HClO₄	perchlorate	ClO₄^-
chloric acid	HClO₃	chlorate	ClO₃^-
chlorous acid	HClO₂	chlorite	ClO₂^-
hypochlorous acid	HClO	hypochlorite	OCl^-

You may be expected to know the IUPAC acceptable name and formula of this polyatomic anion derived from an inorganic base ⁽⁷⁾:
hydroxide : OH^-

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Naming Salts Given the Formula for the Salt

Recall that in the formula of a salt (M_aX_b):

the formula (without charge) of the cation is written first

the formula (without charge) of the anion is written last

The formula of the salt (M_aX_b) tells is it is made up of two ions:

cations (M)

anions (X)

The formula of the salt (M_aX_b) tells us the number of ions present:

number of cations (M) = a

number of anions (X) = b

Recall that if there is only 1 cation present the formula would be MX_b
If only 1 anion is present the formula would be M_aX
If there is only 1 cation and 1 anion present the formula would be MX

If more than one polyatomic cation is present in the salt formula, then the formula of the polyatomic cation is enclosed in parentheses (M):
(M)_(a)X_b

If more than one polyatomic anion is present in the salt formula, then the formula of the polyatomic anion is enclosed in parentheses (X):
M_(a)(X)_b

If the formula of the salt is composed of more than one cation and more than one anion, then the formula would be (M)_a(X)_b

A salt has no overall charge, this means that the total positive charge of all the cations present in the salt's formula is exactly balanced by the total negative charge due to all the anions present in the formula of the salt.

We can use this information in the formula of a salt (M_aX_b) to help us name that salt, as shown in the steps below:

Break the formula of the salt up into two parts:
(i) cation (first part of the formula)

(ii) anion (last part of the formula)

Salt M_aX_b

cation anion

M X

Name the anion present in salt M_aX_b using one of these methods:
(i) name of anion of non-metal element

(ii) recall of formula and name of polyatomic anions

Salt M_aX_b

cation anion

M X^y-

anion name

Determine the individual charge on each anion (X^y-) in salt M_aX_b using either of these methods:
(i) location in periodic table for monoatomic non-metal anions

(ii) recall of formula and name of polyatomic anions

charge on one anion = y-

Determine the total charge on all anions in salt M_aX_b by multiplying the charge on each anion by the number of anions present:
total charge due to all anions = b × y-

Determine the total charge on all cations in salt M_aX_b which will be the same as the total charge of all anions, BUT, with the opposite sign:
total charge due to all cations = -(b × y-)

Determine the individual charge on each cation in salt M_aX_b by dividing the total charge due to all cations by the number of cations (a)
charge on one cation = total charge due to all cations ÷ a

Name the cation based on either of these methods:
(i) monoatomic metal cations: name(charge in parentheses)

(ii) polyatomic cation: name only required

Note that the names of Group 1 and Group 2 metals do not require the charge number to be placed in parentheses after then name of the cation

Assemble the name of the salt remember to leave a space between the name of the cation and the name of the anion

Salt M_aX_b

cation anion

M^x+ X^y-

cation name anion name

Salt M_aX_b
cation	anion
M	X

Salt M_aX_b
cation	anion
M	X^y-
	anion name

Salt M_aX_b
cation	anion
M^x+	X^y-
cation name	anion name

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Worked Example: Naming Salts Composed of Monoatomic Ions

Question 1: Name the salt that has the formula NaI

Solution:

Break the formula of the salt up into two parts:
(i) cation (first part of formula)

(ii) anion (last part of formula)

Salt NaI

cation anion

Na I

Name the anion present in salt NaI using one of these methods:
(i) name of anion of non-metal element : I is the symbol for iodine therefore anion is named iodide

(ii) recall of formula and name of polyatomic anions

Salt NaI

cation anion

Na I^-

iodide

Determine the individual charge on each anion in salt NaI using either of these methods:
(i) location in periodic table for monoatomic non-metal anions : iodine is group 17 element so its charge number is 1-

(ii) recall of formula and name of polyatomic anions

charge on one anion = 1-

Determine the total charge on all anions in salt NaI by multiplying the charge on each anion by the number of anions present:
total charge due to all anions = 1 × 1- = 1-

Determine the total charge on all cations in salt NaI which will be the same as the total charge of all anions, BUT, with the opposite sign:
total charge due to all cations = -(1-) = 1+

Determine the individual charge on each cation in salt NaI by dividing the total charge due to all cations by the number of cations
charge on one cation = 1+ ÷ 1 = 1+

Name the cation based on either of these methods:
(i) monoatomic metal cations: Na is the chemical symbol for sodium, cation is therefore sodium(1+)

(ii) polyatomic cation: name only required

Note that the names of Group 1 and Group 2 elements do not require the charge number to be placed in parentheses after the name of the cation

cation name is therefore sodium

Assemble the name of the salt remembering to leave a space between the name of the cation and the name of the anion

Salt NaI

cation anion

Na⁺ I^-

sodium iodide

NaI has the name sodium iodide

Salt NaI
cation	anion
Na	I

Salt NaI
cation	anion
Na	I^-
	iodide

Salt NaI
cation	anion
Na⁺	I^-
sodium	iodide

Question 2: Name the salt that has the formula FeCl₂

Solution:

Break the formula of the salt up into two parts:
(i) cation (first part of formula)

(ii) anion (last part of formula)

Salt FeCl₂

cation anion

Fe Cl

Name the anion present in salt FeCl₂ using one of these methods:
(i) name of anion of non-metal element : Cl is the symbol for chlorine therefore anion is named chloride

(ii) recall of formula and name of polyatomic anions

Salt FeCl₂

cation anion

Fe Cl^-

chloride

Determine the individual charge on each anion in salt FeCl₂ using either of these methods:
(i) location in periodic table for monoatomic non-metal anions : chlorine is group 17 element so its charge number is 1-

(ii) recall of formula and name of polyatomic anions

charge on one anion = 1-

Determine the total charge on all anions in salt FeCl₂ by multiplying the charge on each anion by the number of anions present:
total charge due to all anions = 2 × 1- = 2-

Determine the total charge on all cations in salt FeCl₂ which will be the same as the total charge of all anions, BUT, with the opposite sign:
total charge due to all cations = -(2-) = 2+

Determine the individual charge on each cation in salt FeCl₂ by dividing the total charge due to all cations by the number of cations
charge on one cation = 2+ ÷ 1 = 2+

Name the cation based on either of these methods:
(i) monoatomic metal cations: Fe is the chemical symbol for iron, cation is therefore iron(2+)

(ii) polyatomic cation: name only required

Note iron can exist as cations with different charge numbers so it requires the charge number to be placed in parentheses after the name of the cation

Recommended cation name is therefore iron(2+)
(iron(II) is not a recommended name, neither is ferrous a recommended name)

Assemble the name of the salt remembering to leave a space between the name of the cation and the name of the anion

Salt FeCl₂

cation anion

Fe²⁺ Cl^-

iron(2+) chloride

The recommended name for FeCl₂ is iron(2+) chloride
(iron(II) chloride is not a recommended name)
(ferrous chloride is not a recommended name)

Salt FeCl₂
cation	anion
Fe	Cl

Salt FeCl₂
cation	anion
Fe	Cl^-
	chloride

Salt FeCl₂
cation	anion
Fe²⁺	Cl^-
iron(2+)	chloride

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Worked Example: Naming Salts Composed of Polyatomic Ions

Question 1: Name the salt that has the formula CuSO₄

Solution:

Break the formula of the salt up into two parts:
(i) cation (first part of formula)

(ii) anion (last part of formula)

Salt CuSO₄

cation anion

Cu SO₄

Name the anion present in salt CuSO₄ using one of these methods:
(i) name of anion of non-metal element

(ii) recall of formula and name of polyatomic anions: SO₄^2- has the name sulfate

Salt CuSO₄

cation anion

Cu SO₄^2-

sulfate

Determine the individual charge on each anion in salt CuSO₄ using either of these methods:
(i) location in periodic table for monoatomic non-metal anions

(ii) recall of formula and name of polyatomic anions: charge on sulfate is 2-

charge on one anion = 2-

Determine the total charge on all anions in salt CuSO₄ by multiplying the charge on each anion by the number of anions present:
total charge due to all anions = 1 × 2- = 2-

Determine the total charge on all cations in salt CuSO₄ which will be the same as the total charge of all anions, BUT, with the opposite sign:
total charge due to all cations = -(2-) = 2+

Determine the individual charge on each cation in salt CuSO₄ by dividing the total charge due to all cations by the number of cations
charge on one cation = 2+ ÷ 1 = 2+

Name the cation based on either of these methods:
(i) monoatomic metal cations: Cu is the chemical symbol for copper, cation is therefore copper(2+)

(ii) polyatomic cation: name only required

Note that the names of Group 1 and Group 2 elements do not require the charge number to be placed in parentheses after the name of the cation

name of cation is therefore copper(2+)

Assemble the name of the salt remembering to leave a space between the name of the cation and the name of the anion

Salt CuSO₄

cation anion

Cu²⁺ SO₄^2-

copper(2+) sulfate

CuSO₄ has the name copper(2+) sulfate
(copper(II) sulfate is not a recommended name)
(cupric sulfate is not a recommended name)
(Note: when people refer to "copper sulfate", they mean copper(2+) sulfate)

Salt CuSO₄
cation	anion
Cu	SO₄

Salt CuSO₄
cation	anion
Cu	SO₄^2-
	sulfate

Salt CuSO₄
cation	anion
Cu²⁺	SO₄^2-
copper(2+)	sulfate

Question 2: Name the salt that has the formula Ca(OH)₂

Solution:

Break the formula of the salt up into two parts:
(i) cation (first part of formula)

(ii) anion (last part of formula)

Salt Ca(OH)₂

cation anion

Ca OH

Name the anion present in salt Ca(OH)₂ using one of these methods:
(i) name of anion of non-metal element

(ii) recall of formula and name of polyatomic anions: OH^- has the name hydroxide

Salt Ca(OH)₂

cation anion

Ca OH^-

hydroxide

Determine the individual charge on each anion in salt Ca(OH)₂ using either of these methods:
(i) location in periodic table for monoatomic non-metal anions

(ii) recall of formula and name of polyatomic anions: charge on hydroxide is 1-

charge on one anion = 1-

Determine the total charge on all anions in salt Ca(OH)₂ by multiplying the charge on each anion by the number of anions present:
total charge due to all anions = 2 × 1- = 2-

Determine the total charge on all cations in salt Ca(OH)₂ which will be the same as the total charge of all anions, BUT, with the opposite sign:
total charge due to all cations = -(2-) = 2+

Determine the individual charge on each cation in salt Ca(OH)₂ by dividing the total charge due to all cations by the number of cations
charge on one cation = 2+ ÷ 1 = 2+

Name the cation based on either of these methods:
(i) monoatomic metal cations: Ca is the chemical symbol for calcium, cation is therefore calcium(2+)

(ii) polyatomic cation: name only required

Note that the names of Group 1 and Group 2 elements do not require the charge number to be placed in parentheses after the name of the cation

name of cation is therefore calcium

Assemble the name of the salt remembering to leave a space between the name of the cation and the name of the anion

Salt Ca(OH)₂

cation anion

Ca²⁺ OH^-

calcium hydroxide

Ca(OH)₂ has the name calcium hydroxide

Salt Ca(OH)₂
cation	anion
Ca	OH

Salt Ca(OH)₂
cation	anion
Ca	OH^-
	hydroxide

Salt Ca(OH)₂
cation	anion
Ca²⁺	OH^-
calcium	hydroxide

Question 3: Name the salt that has the formula (NH₄)₂SO₄

Solution:

Break the formula of the salt up into two parts:
(i) cation (first part of formula)

(ii) anion (last part of formula)

Salt (NH₄)₂SO₄

cation anion

NH₄ SO₄

Name the anion present in salt (NH₄)₂SO₄ using one of these methods:
(i) name of anion of non-metal element

(ii) recall of formula and name of polyatomic anions: SO₄^2- has the name sulfate

Salt Ca(OH)₂

cation anion

NH₄ SO₄^2-

sulfate

Determine the individual charge on each anion in salt (NH₄)₂SO₄ using either of these methods:
(i) location in periodic table for monoatomic non-metal anions

(ii) recall of formula and name of polyatomic anions: charge on sulfate is 2-

charge on one anion = 2-

Determine the total charge on all anions in salt (NH₄)₂SO₄ by multiplying the charge on each anion by the number of anions present:
total charge due to all anions = 1 × 2- = 2-

Determine the total charge on all cations in salt (NH₄)₂SO₄ which will be the same as the total charge of all anions, BUT, with the opposite sign:
total charge due to all cations = -(2-) = 2+

Determine the individual charge on each cation in salt (NH₄)₂SO₄ by dividing the total charge due to all cations by the number of cations
charge on one cation = 2+ ÷ 2 = 1+

Name the cation based on either of these methods:
(i) monoatomic metal cations

(ii) polyatomic cation: NH₄⁺ is most often referred to as ammonium

Note that the names of Group 1 and Group 2 elements do not require the charge number to be placed in parentheses after the name of the cation

name of cation is therefore ammonium

Assemble the name of the salt remembering to leave a space between the name of the cation and the name of the anion

Salt (NH₄)₂SO₄

cation anion

NH₄⁺ SO₄^2-

ammonium sulfate

(NH₄)₂SO₄ has the name ammonium sulfate

Salt (NH₄)₂SO₄
cation	anion
NH₄	SO₄

Salt Ca(OH)₂
cation	anion
NH₄	SO₄^2-
	sulfate

Salt (NH₄)₂SO₄
cation	anion
NH₄⁺	SO₄^2-
ammonium	sulfate

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Footnotes: reference "Nomenclature of Inorganic Chemistry: IUPAC Recommendations 2005" (Red Book)

(1) monoatomic or monotomic or monatomic? The IUPAC document cited above uses monoatomic so we will too!

(2) There are 3 primary IUPAC systems for naming an inorganic compound:
Compositional (stoichiometric) nomenclature : requires no understanding of the structure of the connections within the compound and is the system of nomenclature we will use here in this introduction to IUPAC naming of inorganic salts.
Substitutive nomenclature : requires an understanding of connections within the structure of the compound
Additive nomenclature : requires an understanding of connections within the structure of the compound and this is the most generally applicable system for inorganic compounds

(3) Oxidation state as roman numerals placed in parentheses after name of element is no longer recommended as a naming convention by IUPAC.

(4) Originally the latin form of these elements' names were used with the "ous" ending for the lower oxidation state and the "ic" ending for the higher oxidation state.

(5) The name of the element with the symbol Cs is caesium, but IUPAC also accepts the alternative spelling of cesium.

(6) We are only discussing the monoatomic anions here, O^2-, not polyatomic anions like the dioxide anion and trioxide anions (similarly for other non-metals that form polyatomic ions like sulfur and iodine for example)
Compositional names are not recommended for use with polyatomic ions of elements.
The compositional and additive names of Group 1 oxides follow the example of potassium as shown below:
K₂O dipotassium oxide (potassium oxide)
K₂O₂ potassium dioxide(2-) and additive name: dipotassium (dioxide)
KO₂ potassium dioxide(1-) and additive name monopotassium (dioxide)
KO₃ potassium trioxide(1-) and additive name potassium (trioxide)

(7) To be consistent with the rules for the construction of a formula (order of increasing electronegativity, that is symbol for least electronegative atom written first, symbol for most electronegative element written last), hydroxide should be given the formula HO^- NOT OH^-. However, the formula OH^- for hydroxide is well established and accepted.
Systematic IUPAC names for hydroxide are:

oxidanide (substitutive name : water, H₂O, named as oxidane, negative ion produced by dehydronation (deprotonation) is HO^- hence named as oxidanide)
hydridooxygenate(1-) (additive name)