A systematic method of writing chemical formulas and naming compounds Nomenclature A systematic method of writing chemical formulas and naming compounds

Chemical symbols Symbols are used to represent elements Either one capital letter, or a capital letter with a lower case letter Know names and symbols of elements: 1 – 30, plus Rb, Cs, Sr, Ba, Ag, Au, Cd, Hg, Pt, Sn, Pb, Br, I, and U

Chemical formulas Formulas are used to represent compounds All formulas have more than one symbol Two or more capital letters All chemical names have two words No need to capitalize words in name

I. Binary Ionic nomenclature Binary = two elements Ionic means cation and anion Cations (+ ions) are usually metals Anions (- ions) are usually nonmetals Therefore: Two elements, one metal and one nonmetal

a) naming them Mg = magnesium Cl = chlorine, so write “chloride” Name the metal Name the nonmetal, changing the ending to “ide” Example: name MgCl2 Mg = magnesium Cl = chlorine, so write “chloride” Name is magnesium chloride

Name these NaF Na is sodium F is fluorine, so write fluoride sodium fluoride Al2O3 Al is aluminum O is oxygen, so write oxide aluminum oxide

Name these Ca3P2 Ca is calcium P is phosphorus, so write phosphide calcium phosphide K3N K is potassium N is nitrogen, so write nitride potassium nitride

Name these BaS Ba is barium S is sulfur, so write sulfide barium sulfide SrI2 Sr is strontium I is iodine, so write iodide strontium iodide

Name these Mg3N2 Mg is magnesium N is nitrogen, so write nitride Magnesium nitride BeI2 Be is beryllium I is iodine, so write iodide beryllium iodide

A systematic method of writing chemical formulas and naming compounds Nomenclature A systematic method of writing chemical formulas and naming compounds

I. Binary Ionic nomenclature Binary = two elements Ionic means cation and anion Cations (+ ions) are usually metals Anions (- ions) are usually nonmetals Therefore: Two elements, one metal and one nonmetal

a) naming them Mg = magnesium Cl = chlorine, so write “chloride” Name the metal Name the nonmetal, changing the ending to “ide” Example: name MgCl2 Mg = magnesium Cl = chlorine, so write “chloride” Name is magnesium chloride

Name these BaS Ba is barium S is sulfur, so write sulfide barium sulfide SrI2 Sr is strontium I is iodine, so write iodide strontium iodide

b) Writing formulas Notice: subscripts in the name did not effect the naming of these compounds So, where do the subscripts come from? Why are they there? The subscripts are there to balance charges **ALL IONIC COMPOUNDS ARE NEUTRAL** The subscripts tell us how many of each element are present in the finished formula Example: Al2S3 means 2 aluminums and three sulfurs in one “formula unit”

b) Writing formulas Write the symbol for each ion Balance the charges the element and its charge Balance the charges The total (+) charge must equal the total (-) charge “criss cross” Re-write the formula without any charges

Write the formula for: barium phosphide barium is Ba, the charge is 2+ (column 2A) phosphide was phosphorus, so P; charge is 3- (column 5A) Ba2+P3- Criss-cross to balance charges (2+ with 3-) Ba3P2

Write the formula for: sodium bromide Sodium is Na, the charge is 1+ (column 1A) Bromide was bromine, so Br; charge is 1- (column 7A) Na+Br- Charges are already balanced (1+ with 1-) Re-write as NaBr

Write the formula for: calcium iodide calcium is Ca, the charge is 2+ (column 2A) iodide was iodine, so I; charge is 1- (column 7A) Ca2+I- Criss-cross to balance charges (2+ with -) Ca1I2 Re-write as CaI2

Write the formula for: potassium phosphide potassium is K, the charge is 1+ (column 1A) phosphide was phosphorus, so P; charge is 3- (column 5A) K+P3- Criss-cross to balance charges (+ with 3-) K3P1 Re-write as K3P

Write the formula for: magnesium oxide magnesium is Mg, the charge is 2+ (column 2A) oxide was oxygen, so O; charge is 2- (column 6A) Mg2+O2- Charges are already balanced (2+ with 2-) Re-write as MgO

Special case Zinc (Zn) is always a 2+ ion Silver (Ag) is always a 1+ ion These must be memorized

II. Transition metal ionic nomenclature Transition metals form several possible cations Example: manganese (Mn) is found as 2+, 3+, 4+, 5+, 6+ and 7+ ion! There is no compound just called “manganese oxide” – there are at least four compounds that are different manganese oxides Different charges result in different subscripts

II. Transition metal ionic nomenclature Iron is commonly found as both Fe2+ and Fe3+ Fe2+ is called iron(II) Fe3+ is called iron(III) and,… Cu+ is called copper(I) Cu2+ is called copper(II), etc…

II. Transition metal ionic nomenclature Lead (Pb) and tin (Sn) behave like the transition metals, and therefore follow the same rules Pb2+ is lead(II) Sn4+ is tin(IV) Zinc and silver DO NOT follow these rules, because zinc is always Zn2+ and silver is always Ag+

a) Writing formulas Follow the same rules as the other ionic compounds Iron(II) oxide is Fe2+O2- Charges balance, so formula is FeO Iron(III) oxide is Fe3+O2- Criss cross to balance charges Fe2O3

Write the formula for: vanadium(III) oxide vanadium is V, the charge is 3+ (roman numeral III) oxide was oxygen, so O; charge is 2- (column 6A) V3+O2- Criss cross to balance charges (3+ with 2-) Re-write as V2O3

Write the formula for: Cobalt (II) iodide Cobalt is Co, the charge is 2+ (roman numeral II) iodide was iodine, so I; charge is 1- (column 7A) Co2+I- Criss cross to balance charges (2+ with 1-) Re-write as CoI2

Write the formula for: Lead(IV) sulfide lead is Pb, the charge is 4+ (roman numeral IV) sulfide was sulfur, so S; charge is 2- (column 6A) Pb4+S2- Criss cross to balance charges (4+ with 2-) Re-write as Pb2S4 Reduce subscripts!! PbS2

b) Writing names Same rules as other ionic compounds, except… You must write a roman numeral in parentheses after the name of the metal to show what the positive charge on the metal is Only do this with transition metals And Pb, Sn But not Zn, Ag

Name these NiCl2 Ni is nickel, and it is a transition metal Cl is chlorine, so write chloride nickel( ? ) chloride But, what is the roman numeral? Note: uncriss cross subscripts to determine charges Ni2+Cl- nickel(II) chloride

Name these CuS Cu is copper, and it is a transition metal S is sulfur, so write sulfide copper( ? ) sulfide But, what is the roman numeral? Note: no subscripts, so charges are balanced S is always 2-, so the copper in this compound must be 2+ ! copper(II) sulfide

Name these Cu3N Cu is copper, and it is a transition metal N is nitrogen, so write nitride copper( ? ) nitride But, what is the roman numeral? Note: subscripts, so charges are not balanced copper(I) nitride

Name these Co3P2 Co is cobalt, and is a transition metal P is phosphorus, so write phosphide cobalt(?) phosphide But, what is the roman numeral? Note: un-crisscross subscripts to determine charges Co2+P3- cobalt(II) phosphide

Name these NO! PbO2 Pb is lead, and it behaves like transition metals O is oxygen, so write oxide lead( ? ) oxide But, what is the roman numeral? Note: subscripts show charges are not balanced lead(II) oxide, right? NO!

Name these YES! PbO2 Careful - O is oxide – and is always 2- So the total (-) charge is 4-! So, what is the roman numeral? To balance the 4- charge, you need a 4+ charge lead(IV) oxide, right? YES!

Be careful… When the charges become subscripts that can be reduced Examples: 4+/2- SnO2 is tin(IV) oxide 6+/3- CrP2 is chromium(VI) phosphide 6+/2- MnS3 is manganese(VI) sulfide

A systematic method of writing chemical formulas and naming compounds Nomenclature A systematic method of writing chemical formulas and naming compounds

III. Polyatomic Ionic nomenclature Polyatomic ions are groups of atoms covalently bonded together, that act as a single ion Think of them as lego blocks that have been glued together Each have a name and charge that must be memorized

Polyatomic ions Nitrate: NO31- bicarbonate: HCO31- Image source: wikipedia

Polyatomic ions carbonate: CO32- acetate: C2H3O21- or CH3COO- Image source: wikipedia

Polyatomic ions 1+ ions Ammonium 1- ions Nitrate Hydroxide Bicarbonate NH4+ 1- ions Nitrate NO3- Hydroxide OH- Bicarbonate HCO3- Permanganate MnO4- Acetate C2H3O2-

Polyatomic ions 2- ions Sulfate Carbonate 3- ions phosphate SO42- CO32- 3- ions phosphate PO43-

a) Writing names Same as before: Write the name of the cation Write the name of the anion Simply write the polyatomic ion’s name as it is, without any changes Still only two words in the name

NaNO3 More than two capital letters, so there must be at least one polyatomic ion in the formula Na is sodium, so… The entire “NO3 part” must have a one word name: Nitrate is NO3- sodium nitrate

Al2(SO4)3 More than two capital letters, so there must be at least one polyatomic ion in the formula Al is aluminum, so… The entire SO4 part must have a one word name: Sulfate (SO42-) aluminum sulfate

(NH4)3PO4 Obviously more than two elements Look for polyatomic ions “NH4” is ammonium “PO4” is phosphate Ammonium phosphate

b) Writing formulas Follow the same rules as the other ionic compounds Iron(II) sulfate is Fe2+SO42- Charges balance, so formula is FeSO4

b) Writing formulas Iron(III) sulfate is Fe3+ SO42- Criss cross to balance charges But: we don’t want Fe2SO43 There aren’t 43 oxygens! Use parentheses around polyatomic ion Fe2 (SO4)3

Write the formula for: Chromium(III) carbonate Cr3+ CO32- Crisscross to balance charges Cr2(CO3)3

Write the formula for: Magnesium hydroxide Mg2+ OH- Crisscross to balance charges Mg(OH)2 you need parentheses around the hydroxide because it is a polyatomic ion, even though it has no subscripts of it’s own.

Now – the trickiest ones Name the formula FeSO4 Iron(IV) sulfate? No – the subscript 4 is not from balancing charges! So, how do you know? Look for subscripts from balancing charges to “uncrisscross”

FeSO4 If the 4 were from balancing charges, the formula would have parentheses around the SO – Fe(SO)4 There is no subscript on the Fe – or on the SO4 – from balancing charges So, the charges are balanced Use the “SO4” part to determine the charge on the iron – sulfate has a 2- charge Iron(II) sulfate

Must be memorized… Ag+, Zn2+, no roman numeral when naming Sn, Pb get roman numerals when naming Cr, Mn, Sn, Pb – the total negative charge must be determined to get the positive charge Cannot “uncrisscross” these

A systematic method of writing chemical formulas and naming compounds Nomenclature A systematic method of writing chemical formulas and naming compounds

Types of compounds All compounds are made of two or more elements held together by chemical bonds Ions of opposite charges are held together by ionic bonds Ionic bonding is non-directional There are no “ionic molecules” Formulas of ionic compounds show the ratio of cation to anion Ionic compounds only exist in the solid state, in a 3-D crystal lattice

Types of compounds Covalent compounds are made of elements two or more held together by covalent bonds Covalent bonding is directional Between two individual atoms A group of covalently bonded atoms is referred to as a “molecule” Covalent compounds are also referred to as “molecular” compounds

Binary Molecular Nomenclature Two nonmetals no charges to balance multiple subscripts possible ex: N2O, NO, NO2, N2O4, N2O5

Use prefixes to represent subscripts mono = 1 di = 2 tri = 3 tetra = 4 penta = 5 hexa = 6 hepta = 7 octa = 8 nona = 9 deca = 10

NEVER, EVER, EVER, EVER, EVER, EVER, EVER, USE PREFIXES WITH A METAL!

Rules, continued.. Change second name to end in “ide” do not use prefixes on the first word if the prefix is “mono” always use prefixes on the second name

Examples... CO2 carbon = first word subscript = 1, so no prefix oxide = second word subscript = 2, so prefix = di carbon dioxide

subscript = 1, so no prefix oxide = second word carbon monoxide Examples... CO carbon = first word subscript = 1, so no prefix oxide = second word subscript = 1, so prefix = mono carbon monoxide

Try to name these… N2O4 N2O dinitrogen tetroxide dinitrogen monoxide dinitrogen pentoxide N2O dinitrogen monoxide NO nitrogen monoxide NO2 nitrogen dioxide

Writing formulas... Dinitrogen tetroxide di = 2, so two nitrogen’s tetra = 4, so 4 oxygens N2O4 Note: do NOT reduce subscripts for molecular compounds