chapter 9 chemical names and formulas mr. roberts chemistry level 2
TRANSCRIPT
Chapter 9Chemical Names and Formulas
Mr. RobertsChemistry Level 2
Section 1 – Naming Cations
Group A Elements• Just write name of metal and add “ion” to
ending• Example:
– Na+1 sodium ion– Al+3 aluminum ion
Naming Cations
Group B Elements (transition metals)• Ionic charge will change so write Roman
Numerals in parenthesis after name of metal to indicate charge. (Stock System) – Table 9.2 page 255
Naming Cations• Some post transition element also have charges
that will change.– Ex: Tin and Lead
• Sn+2 Sn+4
• Pb+2 Pb+4
• Some transition metals only have one ionic charge. Therefore you don’t use roman numerals.– Silver Ag+1
– Cadmium Cd+2
– Zinc Zn+2
Naming Anions
• Always have the same charge!– Change suffix with - ide– Ex: F-1 Fluoride ion
O-2 Oxide ion
Polyatomic Ions
• Group of atoms that stay together and have an overall charge
• Usually end with –ate or –ite (one less oxygen)• Ex: (SO3)-2 Sulfite
(SO4)-2 Sulfate
(NH4)+1 ammonium
Section 2 – Writing/Naming Ionic Compounds
Finding the formulas for ionic compounds.• Criss-Cross Method
• Remember…ionic compounds must be expressed in the lowest whole number ratio.
Lose sign
value
Naming Ionic Compounds
• Binary Ionic Compounds (2 ions)– Use rules for naming ions– Ex: Na+1Cl-1 {sodium ion and chloride ion}
NaClSodium Chloride
Naming Ionic Compounds (continued)
• Naming Ternary Ionic Compounds (involving a polyatomic ion group)
• Name it as it appears• Ex: CaCO3 calcium carbonate
Mg3(PO4)2 magnesium phosphate
CaSO4 calcium sulfate• If ammonium or any other polyatomic cation is
reacting with a monatomic anion use binary ionic rules
Naming Group B Ionic Compounds• Rules for naming binary and ternary ionic
compounds apply• Include a roman numeral in parenthesis to
indicate the ionic charge.– Use the reverse of the criss cross method to
determine the charge.– Ex:
Section 3 – Molecular CompoundsNaming Binary molecular compounds (2 nonmetals)• Name the elements in order they appear.• Drop ending of second element and replace with
suffix “ide”.• Use prefixes to indicate # of atoms present
– Table 9.4 page 269
Binary Molecular CompoundsMono = 1Di = 2Tri = 3Tetra = 4Penta = 5Hexa = 6Hepta = 7Octa = 8Nona = 9Deca = 10
Examples:
N2O dinitrogen monoxide
CO2 carbon dioxide
CO carbon monoxideSF6 sulfur hexafluoride
9.4 Naming and Writing Acids• Acid: a compound contain H+ ions.
Anion Ending
Acid Name with Suffix
Acid Ending
Example
- ide hydro________ic acid HCl – hydrochloric acid
- ite ____________ous acid H2SO3 – sulfurous acid
- ate _____________ic acid H2SO4 – sulfuric acid
Examples
HF
HClO2
HClO3
Hydrofluoric Acid
Chlorous Acid
Chloric Acid
Naming and Writing Bases
• Base: a compound containing OH-1
• Named in the same way as other ionic compounds
• Example: NaOH sodium hydroxide
Section 9.5 – The Laws Governing Formulas and Names
We are able to name compounds and write their formulas because they form from elements in
predictable ways
1. The Law of Definite Proportions
• In samples of any chemical compound, the masses of the elements are always in the same proportions.
2. The Law of Multiple Proportions
• Whenever the same two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers.– John Dalton