Chapter 9Chemical Names and Formulas

What is the difference between Cu2O and CuO? Is there any difference? You may think that there is very little difference

between the two, but there is! Naming compounds very specifically is important in order to tell the difference between similar compounds?

Cu2O Red powder fungicide

CuO Black powder Used in batteries

Copper Compounds

What is a cation? Cations – positively charged ion

How many electrons does Group1,2, and 3 lose? Groups 1,2, and 3 lose electrons

Group 1 – lose 1 electron Group 2 – lose 2 electrons Group 3 – lose 3 electrons

Remeber Naming Ions?

Anion – negatively charged ion Groups 5,6, and 7 generally gain electrons

Group 5 – gain 3 electrons Group 6 – gain 2 electrons Group 7 – gain 1 electron

Remember Naming Ions?

Transition metals usually lose electrons, how many electrons they lose depends on the element

Naming Ions

If you actually think about it, it will make sense why some of the transition elements could have two different ions

Ex: Copper (Cu) forms both a +1 and a +2 cation

Why? (Hint: Use the periodic table and electron configuration.) +1 cation: Cu = [Ar] 4s1 3d10 – loses 1 from the

4s subshell + 2 cation: if Cu does not achieve pseudo-

stability, it is [Ar] 4s2 3d9 – will lose the two electrons from the 4s subshell

Naming Ions

Ions composed of more than 1 atom You just have to memorize these Most end in –ite or –ate -ite tells you there is 1 less oxygen

atom than the –ate ending

Polyatomic Ions

what do ionic compounds contain? Ionic compounds – contain a metal and a

nonmetal How do we name a binary ionic compound

(binary means composed of 2 elements)? Place the cation name first, then the anion name Usually add –ide to the end of the anion name

Naming and Writing Formulas for Ionic Compounds

What would Cs2O be? Cesium oxide

NaF? Sodium fluoride

Cu2O (hint: copper has two possible ions! Which one is it?) Copper (I) oxide

SnS2

Tin (IV) Sulfide Mn2O3

Manganese (III) oxide LiCN

Lithium cyanide (NH4)2C2O4

Ammonium oxalate (the –ide ending is usually left out if the anion is a polyatomic ion)

Naming and Writing Formulas for Ionic Compounds

To write a formula for a binary ionic compound, we need to go back to Ch. 7 and balance the charges

Ex: iron (III) oxide Fe+3 O-2

Fe2O3

Ca+2 S-2

Ca2S2….reduce to CaS

Remember crisscross the charge and reduce subscripts to the lowest whole number ratio

Naming and Writing Formulas for Ionic Compounds

Another way…just think about how you would balance the charges out by finding the least common multiple

K+1 N-3

We need a 3 to balance out the +1 on K (1 x 3 =3) and a 1 to balance out the -3 on N (1 x 3) = 3

So K3N

Ba+2 S-2

Both have a 2 charge, they balance each other out

BaS

Naming and Writing Formulas for Ionic Compounds

For polyatomic ions, keep the ion together – balance the overall charge of the ion

Ex: Ca+2 (NO3)-1

Ca(NO3)2

Use parentheses to set off the polyatomic ion only if there is than one of the polyatomic ion

Ex: Li+1 (CO3)-2

Li2CO3 – no parentheses because there is only one polyatomic ion

Ex: NH4+1 (SO3)-2

(NH4)2SO3

Naming and Writing Formulas for Ionic Compounds

What is a binary molecular compound? A compound composed of 2 elements that are

both nonmetals – NOT ions Binary compounds can have 2 elements

composed in various ways – ex: CO and CO2 or NO and N2O so we can’t name them like we did with ionic compounds

We need prefixes…prefixes tell us how many atoms of each element are present in each molecule

Naming and Writing Formulas for Molecular Compounds

Here are a few hints: If there is only 1 atom of the first element, omit the

prefix mono- You will usually add the –ide ending to the second

element Ex: CO

Carbon monoxide Ex: N2O

Dinitrogen monoxide Ex: Cl2O7

Dichlorine heptoxide Ex: BCl3

Boron trichloride

Naming and Writing Formulas for Molecular Compounds

Use the prefixes of each element to write the formula (hint: -mono is left out of the first element if there is only 1 atom)

Ex: carbon monoxide CO

Ex: carbon tetrabromide CBr4

Ex: diphosphorus trioxide P2O3

Ex: iodine heptafluoride IF7

Naming and Writing Formulas for Molecular Compounds

Compound

Covalent

nonmetals

Use prefixes + ide Omit “mono”

for first element if

there is only one

IonicMetal + nonmetal

Cation has one charge

Metal + nonmetal

+ ide ending

Cation has more than 1

chargeMetal (charge) + nonmetal +

ide ending

Summarization