Chemical Formulas, and Nomenclature Names of Elements The most common source for element names is a...

Chemical Formulas, and

Nomenclature

Names of Elements• The most common source for element names is a

property of the elements. EX: nitrogen: Greek for nitron (niter) and genes (to be born). Niter was the name for any naturally occurring substance that contained nitrogen.

• Some elements get their name from their place of discovery, person of honor, or from the mineral from which they are obtained.

Chemical Symbols

• Chemical symbols of the elements are shorthand representations of the elements.

• J. J. Berzelius, a Swedish chemist, is generally given credit for creating the modern symbols for the elements.

• Symbols correspond to the first letter of the name, or the first two letters if needed to distinguish between elements with the same first letter.

Chemical Symbols

• In some cases, the Latin form of the element was used.

EX:

Iron is Fe for ferric

Chemical Formulas

• A chemical formula is a combination of symbols that represents the composition of a compound.

• Chemical symbols are used to indicate types of elements present.

• Subscripts are used to indicate the number of atoms for each element present.

chemical symbols

C8H18

number of atoms of each element

• 8 atoms of carbon

• 18 atoms of hydrogen

Oxidation Numbers of Monatomic Ions

• Because atoms want to reach an octet of valence electrons, the oxidation numbers, positive or negative charges, can be predicted for single atoms (monatomic).

• Metals tend to have positive oxidation numbers. (lose e-)

• Nonmetals tend to have negative oxidations numbers. (gain e-)

1+

2+

most 2+,

but varies

3+ 4+ 3- 2- 1-

0

Oxidation Numbers of Polyatomic Ions

• Polyatomic ions are ions that are made up of two or more atoms.

• Refer to table of Polyatomic ions.• Polyatomic ions generally have the

following endings: “ate” or “ite”EX:

NO2- nitrite

PO4-3 phosphate

Polyatomic Ions

Oxidation Numbers

• The sum of the oxidation numbers in a compound must equal zero.

EX: CaCl2 = Ca+2 + Cl- + Cl-

2 positive charges – 2 negative charges = 0

• The charge on a monatomic ion is its oxidation number.

EX: Ba+2 has an oxidation of +2 Cl- has an oxidation of -1

Oxidation Numbers of Transition Elements

• The oxidation number of a transition element can be determined by two methods.

1. The suffix ending (old system): EX: ferrous is Fe+2

ferric is Fe+3

2. The Roman numeral indicating oxidation.EX: iron (II) is Fe+2

iron (III) is Fe+3

Writing Ionic Formulas

• Remember:• Ionic compounds are composed of metals

and nonmetals.• Ionic compounds are made from the

gaining or losing of electrons and the resulting electrostatic force that holds the ions together.

• The sum of the oxidation numbers in a compound must equal zero.


• When writing formulas, the cation (metal ion) is always written before the anion (nonmetal ion).

• When using polyatomic ions, refer to charge.

There is only one polyatomic cation: NH4

+ that we will focus on.

The remaining are polyatomic anions.


• You can determine the formulas of ionic compounds when given the only the name.

EX: Sodium chloride

Elements: sodium and chlorine

Oxidation: +1 -1

# of each needed

for 0 oxidation: 1 1

Formula: NaCl


EX: Magnesium Iodide

Elements: magnesium and iodine

Oxidation: +2 -1

# of each needed

for 0 oxidation: 1 2

(+2 + -1 + -1)

Formula: MgI2


• Now, let’s include polyatomic ions.

EX: Sodium hydroxide

Elements: Na and OH

Oxidation: +1 -1

# of each needed

For 0 oxidation: 1 1

Formula: NaOH


EX: Aluminum sulfate

Elements: Al and SO4

Oxidation: +3 -2# of each neededFor 0 oxidation: 2 3

(+3 + +3 + -2 + -2 + -2) +6 + -6 = 0

Formula: Al2(SO4)3

Criss Cross Method of Writing Formulas

• Notice a trend between the oxidation/charges of ions and the subscripts of elements.

EX: Mg+2 and Cl- gives

MgCl2

EX: Al+3 and SO4-2 gives

Al2(SO4)3


• This method crosses charges and subscripts to form neutral compounds.

Al +3 and O-2

Al and O

Al2O3

(neutral)


EX:

Lead (II) phosphate

Pb+2 and PO4 -3

Pb and PO4

Pb3(PO4)2

Checking Criss Cross

• You can check to make sure your work is correct by finding the Least Common Multiple (LCM), and calculating charges.

EX: Pb+2 and PO4 -3

LCM is: 6

Pb: 6 ÷ 2 (charge) = 3

PO4: 6 ÷ 3 (charge) = 2

• Ionic compounds need to be in the lowest whole number ratio.

• EX: Pb2(CrO4)4 Pb(CrO4)2

• Exceptions:

1.peroxides: Na2O2, Ag2O2

2.Mercury(I), Mercurous: Needs an overall +2 oxidation to be stable.

EX: Hg2(NO3)2, Hg2Cl2

Nomenclature

• Nomenclature is defined as a naming system.

• Chemistry uses nomenclature to standardize names of chemicals.

• Let’s take a look.

Naming Binary Ionic Compounds

A. Naming binary (composed of two) ionic compounds.

1. Name of cation is given first. The name of the cation is the same as the element.2. Name of anion is given last. The name of the anion is the same as the element, but with an “ide” suffix.

Naming Ionic Compounds

EX: Al2O3

Aluminum and Oxygen

Aluminum oxide

cation anion


EX: AgCl is __________________

Silver chloride

ZnO is ___________________

Zinc oxide

CaBr2 is ___________________

Calcium bromide

Na2O is ___________________

Sodium oxide

Naming Ternary Ionic Compounds

B. Compounds containing a polyatomic ion.

1. Cation rule from binary applies.

2. Anion takes the name of the polyatomic ion as found on the table.

EX: Al2(SO4)3

Aluminum sulfate

EX: Mg(OH)2

Magnesium hydroxide


EX: Li2CO3 is ____________________

Lithium carbonate

Ba(OH)2 is ___________________

Barium hydroxide

Zn(NO3)2 is __________________

Zinc nitrate

KClO3 is ___________________

Potassium chlorate

Naming Transition Element Compounds

• Cation rule applies to transition metals but must also include oxidation state for those transition elements that have more than one oxidation.

• Common elements with more than one oxidation:

Fe, Cu, Mn, Pb, Co, Hg, Sn

New System

• The most common system for naming metals with more than one oxidation is the Roman Numeral system.

• In this system, the oxidation is shown by writing it in parenthesis after the metal name.

EX: Pb+2 = Lead(II)Sn+4 = Tin(IV)Cu+1 = Copper(I)

Classic System• The classic system of naming metals with

more than one oxidation uses Latin (or Greek) root name of element and suffixes to show oxidation.

• “ous” is used for the lesser oxidation.• “ic” is used for the greater oxidation.EX: Pb+2 = Plumbous

Sn+4 = StannicCu+1 = Cuprous

Classic System Root Names

• Iron Fe Ferrous Ferric

• Copper Cu Cuprous Cupric

• Tin Sn Stannous Stannic

• Lead Pb Plumbous Plumbic

• There are transition elements that will retain the element name as found on the periodic table combined with a suffix.

EX: Mercury Hg MercurousMercuric

Cobalt Co CobaltousCobaltic

Manganese Mn ManganousManganic

• How to determine the charge of the metal in an ionic compound:

-Refer to the anion and determine overall negative charge.

-Metal cation must contribute same positive charge.

EX: Fe2O3

1.Oxygen is -2 x the 3 atoms = -6 overall.

2.2 iron atoms at an oxidation of +3 will result in +6 overall.

3.The oxidation of Fe is +3

Transition Metals with One Oxidation

• We only use the Roman Numeral or Classic System only for those metals with more than one oxidation.

• Transition elements with only one possible oxidation will be named with the name of the metal only. (like Group 1, 2, and 13)Zinc (can only be +2)Silver (+1)Cadmium (+2)

• Name each compound using the Roman Numeral System and the Classic System

1. FeO

2. Sn(NO3)4

3. CuCl

4. MnSO4

5. HgBr

6. HgCl2

7. CoCO3

8. Pb(ClO4)4

9. CuSO3

Naming

• Name the following compound:

• Ba(Na)2

Banana

Naming Binary Molecular Compounds

• Unlike ionic compounds, molecular compounds are composed of individual covalently bonded units, or molecules.

• Prefixes are used to indicate number of each type of element in the compound.

• Write the prefixes as indicated on the next slide.

Molecular Prefixes

1 mono- 6 hexa-

2 di- 7 hepta-

3 tri- 8 octa-

4 tetra- 9 nona-

5 penta- 10 deca-


Follow these rules:

1. The less electronegative element is given first. It is given a prefix if it contributes more than one atom to the molecule.


2. The second element is named by combining (a) a prefix indicating the number of atoms contributed by the element, (b) the root of the name of the second element, and, (c) the ending -ide.

3. The o or a at the end of a prefix is usually dropped when the word following the prefix begins with another vowel.EX: monoxide or pentoxide


EX: P4O10

1. P is less e-neg and it has more than one atom in this molecule.

Tetraphosphorus

2. O is named by combining prefix, root name, and ide ending.

decoxide (a is dropped from prefix)

*combine to form: Tetraphosphorus decoxide


EX: SO3 is ____________________

Sulfur trioxide

PBr5 is ____________________

Phosphorus pentabromide

ICl3 is _____________________

Iodine trichloride

H20 is _____________________

Dihydrogen monoxide

Strange Names for Molecules

• ANOL

• BUTANOL

• MORONIC ACID

• CRAPINON

Naming Acids

• Acids are molecular compounds that contain hydrogen bonded to a nonmetal or to a group of polyatomic ions.

• Acids can be either binary or ternary compounds.

• Names of binary acids have the form hydro-…ic acid.

• Names of ternary acids use a series of prefixes and suffixes to specify # of oxygen atoms in the molecule.

Naming Binary Acids

EX: Binary acid: HF is hydrofluoric acid

HCl is hydrochloric acid

Try:

H2S

HI

HBr

Naming Ternary Acids• When naming ternary acids, identify

polyatomic ion in the formula.• For polyions that end in “ate” change the

ending to “ic”. (Something I “ate” made me feel “ic”.

• For polyions that end in “ite” change the ending to “ous”.(A snake b“ite” is poison“ous”)

EX: nitrate nitricnitrite nitroussulfite sulfate

• When naming ternary acids from polyions that have up to four oxygen possibilities:

per-… -ic greatest # of oxygen atoms.

-ic greater

-ous smaller

hypo-…-ous smallest # of oxygen atoms.

*Know all forms of ClO3-1 and IO3

-1

Polyion Acid Formula Acid Name

ClO4-1 HClO4 perchloric acid

ClO3-1 HClO3 chloric acid

ClO2-1 HClO2 chlorous acid

ClO-1 HClO hypochlorous acid• Name:

HIO

HIO2

HIO3

HIO4

Naming Acids

Name the following acids:HClH2SO4

H3PO4

HFHNO3

HNO2

HC2H3O2

HClO2

HBrO3

HClO4

Writing Formulas of Acids

• Acids are molecules that are covalently bonded yet they have properties of ionic compounds so use rules for creating neutral ionic compounds.

• Formulas for acids begin with Hydrogen. The oxidation state for hydrogen is +1.

• Identify if the acid is binary or ternary. If the acid is binary, it will have a “hydro” prefix, all others will be ternary.

Formulas of Binary Acids

• Write H+1 • Identify the monotomic anion by its root

name in the acid.• Determine its charge by following the

oxidation trend for the groups.• Write the element symbol and its negative

oxidation.• Criss Cross charges to create neutral acid

formulas.

EX: hydrosulfuric acid

H+1 S-2

H2SNow Try: hydrochloric acidhydrobromic acidhydrophosphoric acid

hydrofluoric acid

Formulas of Ternary Acids

• Write H+1

• Identify polyion by: 1. ic ate and ous ite suffixes2. prefixes of per and hypo to indicate numbers of oxygen atoms for chlorates and iodates.

• Write formula of polyion including oxidation.

• Criss Cross charges for neutral formula.

EX: sulfuric acidH+1 SO4

-2

H2SO4

Now try:phosphoric acidnitrous acidperchloric acidacetic acidnitric acidsulfurous acidhypoiodous acid

Molecular and Empirical Formulas

• The formulas for compounds that exist as molecules are called molecular formulas.

EX: Hydrogen peroxide, H2O2, consists of two H atoms and two O atoms.

• The atomic ratio of hydrogen peroxide is one to one.

• The simplest formula that would indicate this ratio would be HO. This simple formula is an empirical formula.


• Formulas for ionic compounds are almost always empirical.

EX: NaBr is empirical because it takes one sodium atom to combine with onebromine atom to obtain a neutral

charge.*The exception is Hg+1, it is unstable so an

overall charge of +2 has to be made by two mercurous ions.

Hg2Cl2 and Hg2(NO3)2 are correct.


• C6H12O6 is molecular for Glucose• CH2O is empirical because we could

factor out a six from each subscript.

• CH3COOH is molecular for Acetic Acid• CH2O is empirical (factor out a 2).* Note: Glucose and Acetic Acid are very

different molecules yet they have the same empirical formula.

• Identify each of the following as empirical or molecular. If molecular, make empirical.

1. CH4

2. Ag2SO4

3. C3H9O3

4. N2O2

5. C2H4

6. Hg2(ClO3)2

7. C2H4OH8. N2O5

9. P5O10

In Summary

• A chemical symbol for an element represents one atom of that element when it appears in a formula.

• A chemical formula is a statement in chemical symbols of the composition of one formula unit of a compound. A subscript in a formula represents the relative number of atoms of an element in the compound.

In Summary

• An ion is a charged particle that is formed when an atom gains or loses electrons.

• A polyatomic ion is a stable, charged group of atoms.

• Oxidations numbers for monatomic ions can be predicted from placement on the periodic table.

• In chemical compounds, atoms combine to form neutral charges.

In Summary

• A binary compound is composed of two elements. Its name is the name of the cation followed by the name of the anion modified to end in –ide.

• Some elements have more than one oxidation number. A compound containing such an element is named by showing the oxidation number as Roman numerals in parentheses after the element.

In Summary

• A compound containing a polyatomic ion is named in the same way as a binary compound, except the ending of the polyatomic ion is not changed.

• A molecular formula shows the actual number of each kind of atom in a single molecule of a compound.

In Summary

• An empirical formula represents the simplest whole-number ratio between atoms in a compound.

• A C6H12O6 production.

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