chemical formula and nomenclature

CHEMISTRY

Chemical Formula and Nomenclature

ENGR. YVONNE LIGAYA F. MUSICO

CHEMISTRY

Writing Chemical Formula

CHEMISTRY

CHEMISTRY

Chemical Formula

A representation of the composition of compounds. It contains:

1. The symbol and formula of elements or radicals

2. The number of atoms of each element present written as numerical subscript to the right symbol.

CHEMISTRY

CHEMISTRY

Things to know in writing a Chemical Formula

1. The symbols of elements and radicals

2. Corresponding valence or oxidation numbers

CHEMISTRY

CHEMISTRY

Terminologies

Valence - denotes the number of electrons in the outermost energy level.

- It also describes the combining power of an atom in a compound.

CHEMISTRY

CHEMISTRY

Predicting Ionic Charges

Group 1AGroup 1A::Lose 1 electron to form 1+ ionsLose 1 electron to form 1+ ions

HH++ LiLi++ NaNa++ KK++

CHEMISTRY

CHEMISTRY


Group 2AGroup 2A::Loses 2 electrons to form 2+ ionsLoses 2 electrons to form 2+ ions

BeBe2+2+ MgMg2+2+ CaCa2+2+ SrSr2+2+ BaBa2+2+

CHEMISTRY

CHEMISTRY

Predicting Ionic ChargesGroup 3AGroup 3A:: Loses 3 Loses 3 electrons to form electrons to form 3+ ions3+ ions

BB3+3+ AlAl3+3+ GaGa3+3+

CHEMISTRY

CHEMISTRY

Predicting Ionic ChargesGroup 4AGroup 4A:: Lose 4 Lose 4 electrons or gain electrons or gain 4 electrons?4 electrons?

Neither! Group 3A Neither! Group 3A elements rarely elements rarely form ions.form ions.

CHEMISTRY

CHEMISTRY

Predicting Ionic ChargesGroup 5AGroup 5A:: Gains 3 Gains 3 electrons to form electrons to form 3- ions3- ions

NN3-3-

PP3-3-

AsAs3-3-

Nitride

Phosphide

Arsenide

CHEMISTRY

CHEMISTRY


Group 6AGroup 6A:: Gains 2 Gains 2 electrons to form electrons to form 2- ions2- ions

OO2-2-

SS2-2-

SeSe2-2-

Oxide

Sulfide

Selenide

CHEMISTRY

CHEMISTRY

Predicting Ionic ChargesGroup 7AGroup 7A:: Gains 1 Gains 1 electron to form electron to form 1- ions1- ions

FF1-1-

ClCl1-1-

BrBr1-1-Fluoride

Chloride

Bromide

II1-1- Iodide

CHEMISTRY

CHEMISTRY


Group 8AGroup 8A:: Stable Stable Noble gases Noble gases do do notnot form ions! form ions!

CHEMISTRY

CHEMISTRY

Predicting Ionic ChargesGroups 3 - Groups 3 - 1212::

Many transition elements Many transition elements have more than one possible oxidation have more than one possible oxidation state.state.Iron(II) = Fe2+ Iron(III) = Fe3+

CHEMISTRY

CHEMISTRY

Predicting Ionic ChargesGroups 3 - Groups 3 - 1212::

Some transition elements Some transition elements have only one possible oxidation state.have only one possible oxidation state.

Zinc = Zn2+ Silver = Ag+

CHEMISTRY

CHEMISTRY

Terminologies

Radicals – group of elements which act as one or single atom in chemical reaction and show definite valence.

Example:

Sulfate ion (SO4-2)

Ammonium ion (NH4+1)

CHEMISTRY

Rules in Writing Chemical Formula

CHEMISTRY

CHEMISTRY


RULE 1 (CRISS-CROSS RULE) Chemical compounds are electrically charged, the

total number of positive charge is equal to the number of negative charges; hence, the valence of positive entity (ion or radical) equals subscript of negative entity.

The sum of the positive and the negative valence should add up to zero.

The positive ion is written first followed by the negative.

CHEMISTRY

CHEMISTRY

Example: Aluminum sulfide

1. Write the formulas for the cation and anion, including CHARGES!

AlAl3+3+ SS2-2-2. Check to see if charges are balanced.

3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.

Not balanced!

22 33

AlAl SS22 33

The Chemical Formula

CHEMISTRY

CHEMISTRY


RULE 2

When valence number is 1, subscript is not written

Example:

Sodium Chloride - Na+1Cl-1 → NaCl

CHEMISTRY

CHEMISTRY


RULE 3

When the oxidation numbers of both elements are numerically equal but greater than 1, the subscript are not also written.

Example:

Calcium Oxide - Ca+2O-2 → CaO

Exception: Benzene - C6H6

CHEMISTRY

CHEMISTRY

Example: Magnesium carbonate


MgMg2+2+ COCO332-2-2. Check to see if

charges are balanced.

They are balanced!

MgMgCOCO33

Chemical Formula

CHEMISTRY

CHEMISTRY

Example: Aluminum phosphate


AlAl3+3+ POPO443-3-2. Check to see if charges are

balanced.

They ARE balanced!AlAlPOPO44

Chemical Formula

CHEMISTRY

CHEMISTRY


RULE 4 All radicals take more than one (the subscript is 2 or more)

must be enclosed in parenthesis ().

Example:

Ammonium Sulfate - NH4+1SO4-2 → (NH4)2SO4

CHEMISTRY

CHEMISTRY

Example: Barium nitrate


BaBa2+2+ NONO33--

2. Check to see if charges are balanced.


Not balanced!

( )( )22

BaBa NONO33( )( )22

Chemical Formula

CHEMISTRY

CHEMISTRY

Example: Zinc hydroxide


ZnZn2+2+ OHOH--2. Check to see if charges are balanced.


Not balanced!

( )( )

22

ZnZn OHOH22

( )( )

Chemical Formula

CHEMISTRY

CHEMISTRY


RULE 5 All subscript must be reduced to lowest terms (except for

molecular or covalent compounds)

Example:

Tin (IV) Oxide - Sn+4O2-2 → Sn2O4

→ SnO2

CHEMISTRY

Formulas of Binary Ionic Compounds Containing

Metals with Variable Valence Oxidation Number or Valence

CHEMISTRY

CHEMISTRY

A. Stock System

Roman numeral indicated after the name of the metal represents the oxidation number (valence) of metal.

Example:

Tin (IV) Chloride - Sn+4Cl-1 → SnCl4

Tin (II) Chloride - Sn+2Cl-1 → SnCl2

CHEMISTRY

CHEMISTRY

Example: Iron(III) chloride


FeFe3+3+ClCl--2. Check to see if charges are balanced.


Not balanced!

33

FeFeClCl33


CHEMISTRY

CHEMISTRY

Example: Iron(II) chloride




Not balanced!

22

FeFeClCl22


CHEMISTRY

CHEMISTRY

B. Classical or Conventional System

The ic and ous ending are added to the line stem or root word of the Latin name of the metal

The ic ending indicates higher oxidation number or valence

The ous ending indicates lower oxidation number or valence

CHEMISTRY

CHEMISTRY

B. Classical or Conventional System

Example:

Stannic Chloride - Sn+4Cl-1 → SnCl4

Stannous Chloride - Sn+2Cl-1 → SnCl2

CHEMISTRY

CHEMISTRY

Example: Ferric chloride




Not balanced!

33

FeFeClCl33


CHEMISTRY

CHEMISTRY

Example: Ferrous chloride




Not balanced!

22

FeFeClCl22


CHEMISTRY

Formulas of Binary Molecular or Covalent

Compounds (Containing 2 Non-metals)

CHEMISTRY

CHEMISTRY

Rule 1

The Greek prefix mentioned before the name of the non-metals are written as subscripts of the non-metals.

Example:

Dinitrogen Pentoxide → N2O5

CHEMISTRY

CHEMISTRY

Rule 2

If prefix is mono, it is not mentioned at the start of the name, only the second portion.

Example:

Phosphorous Petachloride → PCl5

Carbon Monoxide → CO

CHEMISTRY

CHEMISTRY

Greek Prefixes Used in Naming Binary Molecular Compounds

Number of Atoms

Prefix Number of Atoms

Prefix

1 mono 6 hexa

2 di 7 hepta

3 tri 8 octa

4 tetra 9 nona

5 penta 10 deca

CHEMISTRY

CHEMISTRY

Try These

Write the chemical formula of the followingAluminum and carbonateCopper II and sulfateSilver phosphateLead II chlorideAmmonium acetate

CHEMISTRY

CHEMISTRY

Answers

Al2(CO3)3

CuSO4

Ag3PO4

PbCl2NH4C2H3O2

CHEMISTRY

Formulas of Acids

CHEMISTRY

CHEMISTRY

A. Binary Acids

Solutions of compounds consisting of hydrogen and non-metal.

The name starts with hydro and the ending ic attached to the acid forming element followed by the word acid.

The formula H followed by the other non-metal

CHEMISTRY

CHEMISTRY

A. Binary Acids

Example:

Hydrochloric Acid - H+Cl-1 → HCl

Hydrosulfuric Acid - H+S-2 → H2S

CHEMISTRY

CHEMISTRY

B. Ternary Acids or Oxyacids

Those containing, H, O, and acid forming element.

The names do not have prefix hydro in their name terminate in ous or ic.

IC – contains more oxygen → salt or radical ends in ate

OUS - contains less oxygen → salt or radical ends in ite

CHEMISTRY

CHEMISTRY


The formula starts with H+1 followed by the radical

H+1 (NMO-) polyatomic ion

CHEMISTRY

CHEMISTRY


Example:

Nitric Acid - H+1 NO3-1

→ HNO3

Nitrous Acid - H+1 NO2-1

→ HNO2

CHEMISTRY

Nomenclature (Naming Compounds)

CHEMISTRY

Rules in Naming Compounds

CHEMISTRY

CHEMISTRY

I. Binary Ionic Compounds

Containing 2 different elements Metal and Non-metal

The name ends in ide

CHEMISTRY

CHEMISTRY


Example:

NaF – Sodium Fluoride

KI – Potassium Iodide

Name of metal + stem name of non metal + ide

A. Binary Ionic Compounds containing a metal with fixed valence (IA and IIA metals and Al, Zn, Ag)

CHEMISTRY

CHEMISTRY


Example:

SnF4 – Tin (IV) Flouride

SnF2 – Tin (II) Flouride

Name of metal (valence in Roman numeral) + stem name of non metal + ide

B. Binary Ionic Compounds containing a metal with variable valence

1. Stock System – Roman numeral enclosed in the parenthesis is written immediately following the name of the metal to indicate the valence of the metal.

CHEMISTRY

CHEMISTRY


Example:

SnF4 – Stannic Flouride

SnF2 – Stannous Flouride

B. Binary Ionic Compounds containing a metal with variable valence

2. Classical (Old) Method – name of metal is modified with ending ic for higher valence and ous for lower valence.

CHEMISTRY

CHEMISTRY


Example:

NH4I – Ammonium Iodide

KCN – Potassium Cyanide

Ca(OH)2 – Calcium hydroxide

Exception using ide endings – Hydroxides (OH), cyanide (CN) and ammonium (NH4) compounds are named with

ide ending although they are not.

CHEMISTRY

CHEMISTRY

II. Binary Molecular Compounds

Example:

P2O4 – Diphosphorous pentaoxide or pentoxide

PCl3 – Phosphorous trichloride

Greek prefix + name of the first non-metal + Greek prefix + stem of name of second non-metal + ide

(Containing 2 non-metals) Greek prefixes are used to indicate the number of atoms.

The prefix mono is dropped at the start of the name.

CHEMISTRY

CHEMISTRY

III. Binary Molecular Compounds Containing Hydrogen listed as the First Element

Example:

HF – Hydrogen Fluoride

HCl – Hydrogen Chloride

Hydrogen + stem of name of non-metal + ide

They are named without using Greek numerical prefixes

CHEMISTRY

CHEMISTRY

IV. Binary Acids

Example:

HCl (in water solution) – Hydrochloric acid

HF (in water solution) – Hydroflouric acid

Hydro + stem of name of non-metal + ic ending + acid

Water solutions of molecular compounds composed of hydrogen and another non-metal except oxygen.

CHEMISTRY

CHEMISTRY

V. Ternary Acids (OXY acids)

Example:

H3PO4 – Phosphoric acid

H2PO3 – Phosphorous acid

Stem of name of non-metal + ic or ous ending + acid

Name end in ous or ic OUS – less oxygen IC – more oxygen

CHEMISTRY

CHEMISTRY

V. Ternary Acids (OXY acids)

Example:

HClO – Hypochlourous acid

HClO2 – Chlorous acid

HClO3 – Chloric acid

HClO4 – Perchloric acid

When there are more than two oxy acids of the same element, the acid wherein the non-metal exhibits a lower valence than the ous acid uses the prefix hypo and suffix ous + the word acid

The acid wherein the non-metal exhibits a higher valence than the ic acid uses the prefix per and the suffix ic + acid

CHEMISTRY

CHEMISTRY

VI. Ternary Compounds

Example:

Al(NO3)3 – Aluminum Nitrate

NaNO2 – Sodium Nitrite

The name ends in ite for less oxygen, ate for more oxygen

CHEMISTRY

CHEMISTRY

Try These

Name the following compoundsK2S

CaCO3

MnCl4HI

CHEMISTRY

CHEMISTRY

ANSWERS

K2S potassium sulfide

CaCO3 calcium carbonate

MnCl4 manganese IV chloride

HI hydroiodic acid or hydrogen iodide

CHEMISTRY

CHEMISTRY

Try These

Name the following compoundsPCl3CCl4COCO2

CHEMISTRY

CHEMISTRY

ANSWERS

PCl3 phosphorus trichloride

CCl4 carbon tetrachloride

CO carbon monoxideCO2 carbon dioxide

CHEMISTRY

Empirical and Molecular Formula

CHEMISTRY

CHEMISTRY

Calculating Formula Mass

Calculate the formula mass of magnesium Calculate the formula mass of magnesium carbonate, MgCOcarbonate, MgCO33..

24.31 g + 12.01 g + 3(16.00 g) 24.31 g + 12.01 g + 3(16.00 g) ==

84.32 g84.32 g

CHEMISTRY

CHEMISTRY

Calculating Percentage Composition

Calculate the percentage composition of Calculate the percentage composition of magnesium carbonate, MgCOmagnesium carbonate, MgCO33..

From previous slide:From previous slide:24.31 g + 12.01 g + 3(16.00 g) = 24.31 g + 12.01 g + 3(16.00 g) = 84.32 g84.32 g 24.31

100 28.83%84.32

Mg 12.01

100 14.24%84.32

C

48.00100 56.93%

84.32O

100.00

CHEMISTRY

CHEMISTRY

Formulas

molecular formula = (empirical formula)n [n = integer]

molecular formula = C6H6 = (CH)6

empirical formula = CH

Empirical formula: the lowest whole number ratio of atoms in a compound.

Molecular formula: the true number of atoms of each element in the formula of a compound.

CHEMISTRY

CHEMISTRY

Formulas (continued)

Formulas for Formulas for ionic compoundsionic compounds are are ALWAYSALWAYS empirical (lowest whole empirical (lowest whole number ratio).number ratio).Examples:Examples:

NaCl MgCl2 Al2(SO4)3 K2CO3

CHEMISTRY

CHEMISTRY

Formulas (continued)

Formulas for Formulas for molecular compoundsmolecular compounds MIGHTMIGHT be empirical (lowest whole be empirical (lowest whole number ratio).number ratio).

Molecular:Molecular:

H2O

C6H12O6 C12H22O11

Empirical:

H2O

CH2O C12H22O11

CHEMISTRY

CHEMISTRY

Empirical Formula Determination

1. Base calculation on 100 grams of compound.

2. Determine moles of each element in 100 grams of compound.

3. Divide each value of moles by the smallest of the values.

4. Multiply each number by an integer to obtain all whole numbers.

CHEMISTRY

CHEMISTRY

Empirical Formula Determination

Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid?

49.32 14.107

12.01

g C mol Cmol C

g C

6.85 16.78

1.01

g H mol Hmol H

g H

43.84 12.74

16.00

g O mol Omol O

g O

CHEMISTRY

CHEMISTRY

Empirical Formula Determination(part 2)

4.1071.50

2.74

mol C

mol O

6.782.47

2.74

mol H

mol O

2.741.00

2.74

mol O

mol O

Divide each value of moles by the smallest Divide each value of moles by the smallest of the values.of the values.

Carbon:Carbon:

HydrogenHydrogen::

OxygenOxygen::

CHEMISTRY

CHEMISTRY

Empirical Formula Determination(part 3)

Multiply each number by an integer to Multiply each number by an integer to obtain all whole numbers.obtain all whole numbers.

Carbon: 1.50Carbon: 1.50 Hydrogen: 2.50Hydrogen: 2.50 Oxygen: 1.00Oxygen: 1.00x 2 x 2 x 2

33 55 22

Empirical formula: C3H5O2

CHEMISTRY

CHEMISTRY

Finding the Molecular Formula

The empirical formula for adipic acid The empirical formula for adipic acid is Cis C33HH55OO22. The molecular mass of . The molecular mass of adipic acid is 146 g/mol. What is the adipic acid is 146 g/mol. What is the molecular formula of adipic acid?molecular formula of adipic acid?

1. Find the formula mass of 1. Find the formula mass of CC33HH55OO22

3(12.01 g) + 5(1.01) + 2(16.00) = 3(12.01 g) + 5(1.01) + 2(16.00) = 73.08 g73.08 g

CHEMISTRY

CHEMISTRY



3(12.01 g) + 5(1.01) + 2(16.00) = 3(12.01 g) + 5(1.01) + 2(16.00) = 73.08 g73.08 g

2. Divide the molecular mass by 2. Divide the molecular mass by the mass given by the emipirical the mass given by the emipirical formula.formula.

1462

73

CHEMISTRY

CHEMISTRY



3(12.01 g) + 5(1.01) + 2(16.00) = 3(12.01 g) + 5(1.01) + 2(16.00) = 73.08 g73.08 g146

273

3. Multiply the empirical formula by 3. Multiply the empirical formula by this number to get the molecular this number to get the molecular formula.formula.

(C(C33HH55OO22) x 2 ) x 2 ==

CC66HH1010OO44

CHEMISTRY

Question or Comments?

chemical formula and nomenclature

Documents