Molecules and compounds nomenclature chapter 5
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Molecules and Compounds (Nomenclature) Chapter 5. Tro, 2 nd ed. Molecules and Compounds. Pair up and look up this law and then write it in your own words to share with the rest of the class. Give examples other than what is in the textbook. Law of Constant Composition.

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Molecules and Compounds (Nomenclature) Chapter 5

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Molecules and compounds nomenclature chapter 5

Molecules and Compounds(Nomenclature)Chapter 5

Tro, 2nd ed.


Molecules and compounds

Molecules and Compounds

Pair up and look up this law and then write it in your own words to share with the rest of the class. Give examples other than what is in the textbook.

Law of Constant Composition


How to learn nomenclature

HOW TO LEARN NOMENCLATURE

Memorize, memorize, memorize!

Memorize the rules for naming

Memorize names of ions

Memorize some acid names and some organic names


Types of compounds and naming rules

Types of Compounds and Naming Rules

Compound

Ionic (formula unit) Covalent (molecule)

SaltsHydrates OtherBinary (Ternary)Organic Acids Other

Binary

Polyatomic Ions

You will learn all the rules for ionic, hydrates, covalent binary, and only specific common names, organic compounds and acids.


Common and systematic names

Common and Systematic Names

Chemical nomenclature is the system of names that chemists use to identify compounds. Two classes of names exist: common names and systematic names.

Common names are arbitrary names.

They are not based on the composition of the compound.

They are based on an outstanding chemical or physical property.

Common names that you need to memorize: acetylene, ammonia, water, baking soda, cane sugar, epsom salts, grain alcohol, laughing gas, lye, muriatic acid, table salt, vinegar, washing soda, and wood alcohol. (common name, formula and systematic name)


Molecules and compounds nomenclature chapter 5

Ammonia, NH3


Molecules and compounds nomenclature chapter 5

Chemists prefer systematic names.

Systematic names precisely identify the chemical composition of the compound.

The present system of inorganic chemical nomenclature was devised by the International Union of Pure and Applied Chemistry (IUPAC).


The formula for most elements is the symbol of the element

SodiumNa

PotassiumK

ZincZn

ArgonAr

MercuryHg

LeadPb

CalciumCa

The formula for most elements is the symbol of the element.


Molecules and compounds nomenclature chapter 5

These 7 elements are found in nature as diatomic molecules.

HydrogenH2

NitrogenN2

OxygenO2

Fluorine F2

ChlorineCl2

BromineBr2

Iodine I2


Molecules and compounds nomenclature chapter 5

If one or more electrons are removed from a neutral atom a positive ion is formed. A positive ion is called a cation.

A charged particle known as an ion can be produced by adding or removing one or more electrons from a neutral atom.

remove e-

neutral atom

cation


Monatomic ions

MONATOMIC IONS:

Metals always lose electrons to form positive ions, called cations

If element forms only one cation, we name it by its element name:

Na+ = sodium ion Al3+ = aluminum ion

If a transition metal can form more than one cation, add ion’s charge in Roman numerals to the name.

Fe2+ is iron(II) ion and Fe3+ is iron(III) ion.

(Old names, ferrous and ferric.)


Molecules and compounds nomenclature chapter 5

If one or more electrons are added to a neutral atom a negative ion is formed. A negative ion is called an anion.

A charged particle known as an ion can be produced by adding or removing one or more electrons from a neutral atom.

add e-

neutral atom

anion


Monatomic ions1

MONATOMIC IONS:

Nonmetal atoms gain electrons to form negative ions, called anions

Take the root of the element name and add “-ide”

Cl- = chloride ionSe2- = selenide ion

N3- = nitride ion

Most often ions are formed when metals combine with nonmetals. (Exception is NH4+ with anion.)

The charge on an ion can be predicted from its position in the periodic table.


Molecules and compounds nomenclature chapter 5

elements of Group VIIA have a-1 charge

elements of Group VIA have a -2 charge

elements of Group VA have a-3 charge

elements of Group IA have a +1 charge

elements of Group IIA have a+2 charge


Naming ionic compounds

NAMING IONIC COMPOUNDS:

Always put cation before anion in formula. Name of compound is just cation name followed by anion name.

MgF2 is Mg2+ and F- = magnesium fluoride

FeBr3 is Fe3+ and Br- = iron(III) bromide

What is the formula for silver carbonate?

Silver ion is Ag+ and carbonate CO32-

- have to balance charges, so need 2 Ag+ for each CO32- = Ag2CO3

Generic: Ma+bNb-a criss-cross rule

However, if a = b, then both = 1 by definition for lowest ratio

Figure out the charge on each x:

ZnX, NH4X, (NH4)2X, Al2X3, X2(SO3)3


Molecules and compounds nomenclature chapter 5

Write the formula of barium phosphide.

The lowest common multiple of +2 and –3 is 6

Step 1. Write down the formulas of the ions.

Ba2+P3-

Step 2. Combine the smallest numbers of Ba2+ and P3- so that the sum of the charges equals zero.

The cation is written first.

The anion is written second.

3(Ba2+) +2(P3-) = 0

3(2+) + 2(3-) = 0

The correct formula is Ba3P2


Naming compounds containing polyatomic ions

Naming Compounds Containing Polyatomic Ions

A polyatomic ion is an ion that contains two or more elements.

Compounds containing polyatomic ions are composed of three or more elements.

They usually consist of one or more cations combined with a negative polyatomic ion.

When naming a compound containing a polyatomic ion, name the cation first and then name the anion.


Molecules and compounds nomenclature chapter 5

The ions are what isactually present.

This is the way theformula is written.


Elements that form more than one polyatomic ion with oxygen

phosphite

phosphate

nitrite

nitrate

Elements that Form More than One Polyatomic Ion with Oxygen

Anions ending in -atealways contain more oxygen than ions ending in -ite.


Molecules and compounds nomenclature chapter 5

One group of ionic compounds that contains all nonmetals is the ammonium salts. Try to write formulas for ammonium sulfate and ammonium phosphate.


Anions with hydrogen

ANIONS WITH HYDROGEN

Some anions have picked up one or two hydrogen ions. Old naming rules put “bi” in front of the anion name. IUPAC uses hydrogen or dihydrogen:

CO32- with one H+ added is HCO3-

Carbonate ion becomes hydrogen carbonate ion.

Name these: PO43-, HPO42-, H2PO4-


Molecules and compounds nomenclature chapter 5

hydroxide

cyanide

hydrogen sulfide

peroxide

Four polyatomic ions that do not use the –ate/ite system.


Molecules and compounds nomenclature chapter 5

mercury(I)

ammonium

hydronium

There are three common positively charged polyatomic ions.


Molecules and compounds nomenclature chapter 5

Divide the formula into cation(s) and anion. Name each.

For example KHSO4 is K+ and HSO4-.

MgNH4PO4 is Mg2+, NH4+ and PO43-.


Molecules and compounds nomenclature chapter 5

(So you can see relationship between anions and acids.)


Binary compounds

Binary Compounds

Binary compounds contain only two different elements. There are four main types, listed in following slides.

  • Binary Ionic Compounds Containing a Metal Forming Only One Type of Cation (salts)

    Binary ionic compounds consist of a metal combined with a non-metal.

    The chemical name is composed of the name of the metal followed by the name of the nonmetal which has been modified to an identifying stem plus the suffix –ide.

    Using this system the number of atoms of each element present is notexpressed in the name.

    Practice: CaC2, MgBr2, Al2O3, NaH

    (calcium carbide, magnesium bromide, aluminum oxide, sodium hydride)


Binary compounds1

Binary Compounds

B. Binary Ionic Compounds Containing a MetalThat Can Form Two or More Types of Cations (still salts)

The chemical name is composed of the name of the metal with its charge in Roman numerals, followed by the name of the nonmetal which has been modified to an identifying stem plus the suffix –ide.

Using this system the number of atoms of each element present is not expressed in the name.

Practice: FeS, CuCl2, SnF2, Mn3(PO4)5

(iron (II) sulfide, tin(II) fluoride, manganese (V) phosphate)


Molecules and compounds nomenclature chapter 5

Ion Names: Classical System

2+

2

Lower Charge Higher Charge

This is for information and for homework only; classical names will not be on quiz or test unless part of a common name that’s required.


Binary compounds2

Binary Compounds

C. Binary Compounds Containing Two Nonmetals (Binary Covalent) Compounds between nonmetals are molecular, not ionic.

In a compound formed between two nonmetals, the element that more electropositive (least electronegative) is named first.

Rules for naming:

1. Give Greek prefix (to indicate number of atoms of first element) to name of first element. Don’t use mono prefix for first element.

2. Give Greek prefix (to indicate number of atoms of second element) to root of element name, then add -ide

Example: N2O3 is dinitrogen trioxide.

Exception: hydrogen never has prefix.


Greek prefixes

Greek Prefixes

mono = 1 di = 2

tri = 3 tetra = 4

penta = 5hexa = 6

hepta = 7 octa = 8

nona = 9deca = 10


Binary compounds3

Binary Compounds

C. Binary Compounds Containing Two Nonmetals (Binary Covalent)Examples

N2O3, PCl5, Cl2O7, CCl4, CO, CO2, PI3, H2S

Dinitrogen trioxide

Phosphorous pentachloride (not mono-)

Dichlorine heptoxide

Carbon tetrachloride

Carbon monoxide

Carbon dioxide

Phosphorous triiodide

Hydrogen sulfide (hydrogen never gets a prefix)

Now try: CS2, H2O, N2O4, SF2, SiCl2, P2O5, phosphorous trichloride, dichlorine oxide


Binary compounds4

Binary Compounds

D. Acids Derived from Binary Compounds

Certain binary hydrogen compounds, when dissolved in water, form solutions that have acid properties.

The aqueous solutions of these compounds are given acid names.

The acids names are in addition to their –idenames.

Hydrogen is typically the first element of a binary acid formula.


Molecules and compounds nomenclature chapter 5

binary hydrogen compound like HCl is called hydrogen chloride (not an acid yet).

Acid sol.

water

Acid Formation

Now it’s hydrochloric acid.


Binary compounds5

Binary Compounds

D. Acids Derived from Binary Compounds

To name binary acids write the symbol of hydrogen first. After hydrogen write the symbol of the second element.

Place the prefix hydro- in front of the stem of the nonmetal name. Place the suffix -ic after the stem of the nonmetal name.

Practice: HCl, H2S, HI

(hydrochloric acid, hydrosulfuric acid, hydroiodic acid)


Molecules and compounds nomenclature chapter 5

D.

A.

C.

B.


Molecules and compounds nomenclature chapter 5

The other element is usually a nonmetal, but it can be a metal.

The first element listed in the formula is hydrogen.

The remainingelements include oxygen and form a polyatomic ion.

The word acid in the name indicates the presence of hydrogen.

Oxy-acids contain hydrogen, oxygen and one other element.

Hydrogen in an oxy-acid is not expressed in the acid name.

More Acids


Molecules and compounds nomenclature chapter 5

indicates hydrogen

contains hydrogen

contains sulfur

contains oxygen

sulfuric acid

This is one of the six acids you have to know.


Molecules and compounds nomenclature chapter 5

(If you add HCl to the ones marked by arrows, you have your total list of acids.)


Your acids

Your Acids

An acid is a substance that forms H+ when dissolved in water

Some are strong acids, that means all the H+ dissolves and dissociates from the anion

Some acids are weak, meaning very little H+ dissociates, although the cmpd dissolves

Forget sections in text: just learn these!

Hydrochloric acid, sulfuric acid, and nitric acid are strong acids: HCl(aq), H2SO4(aq), HNO3(aq)

Acetic acid, carbonic acid, phosphoric acid are weak acids: HC2H3O2(aq), H2CO3(aq), H3PO4(aq)


Your organic compounds

Your Organic Compounds

No naming rules – just learn formulas and names.

CH4 methane, C3H8 propane, C8H18 octane, CH3OH methanol, CH3CH2OH ethanol, C6H6 benzene, CH3COOH acetic acid (organic method), CH3NH2 aminomethane, C6H12O6 glucose, C12H22O11 sucrose, and C2H2, ethyne


Hydrates not in book also a good review of ionic names

HYDRATES: (not in book) Also a good review of ionic names!

If an ionic compound is a hydrate, it will have *H2O in the formula, like MgCO3*6 H2O

Name the ionic compound part using ionic naming rules, then give the Greek prefix for the number of water molecules and add the word hydrate:

MgCO3*6H2O is magnesium carbonate hexahydrate


Hydrates not in book also a good review of ionic names1

HYDRATES: (not in book) Also a good review of ionic names!

Examples: you name the following (notice their common names)

gypsum CaSO4*2 H2O

epsom salts MgSO4*7 H2O

washing soda Na2CO3*10 H2O

bluestone CuSO4*5 H2O

Calcium sulfate dihydrate

Magnesium sulfate heptahydrate

Sodium carbonate decahydrate

Copper(II) sulfate pentahydrate


Formula mass

Formula Mass

As each element’s atom has mass in amu on the Periodic Table, so do molecules and formula units.

Formula mass is the sum of the atomic masses of the atoms in the chemical formula.

Practice: water, sodium chloride, acetic acid


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