Chemical Names and Formulas Notes

Chemical Names and Formulas
 Key Vocabulary
Monoatomic Ion – Ions formed from a single atom
Binary compound – Compounds composed of two elements
Nomenclature – the “naming system” of binary ionic compounds
Oxyanion – polyatomic ions that contain oxygen
Salt – an ionic compound composed of a cation and the anion from an acid
Chemical Formulas
Subscripts after an elemental symbol represent the number of atoms of the
element in the compound
Molecular formulas represent how many atoms of each element are in a compound.
(C2H8, H2O, C6H12O6)
Ionic formulas show the simplest ratio, cations to anions, of atoms in the lattice
Parenthesis are used around a polyatomic ion in a chemical formula
Examples Al2(SO4)3, Cu(PO4)2, Sr(NO3)2
Monoatomic Ions
– Ions formed from a single atom
Group 1 elements may lose one electron = 1+
Group 2 elements may lose two electrons = 2+
Group 13 elements may lose three electrons = 3+
Group 17 elements may gain one electron = 1Group 16 elements may gain two electrons = 2Group 15 elements may gain three electrons = 3Transition metals have various possibilities (no pattern)
Naming monatomic Ions
Monatomic cations are simply called by the element’s name
*the stock system is used when there is more than one possibility for an
element (more on this later)
Monatomic anions end in IDE such as Fluorine – Fluoride, Oxygen – Oxide
(reference table 1 on page 221)
Binary Ionic Compounds
1. Write the symbols for the ions with the cation first (Al3+ O2-)
2. Cross over the charges writing the charge of one ion as the subscript for the other
ion (Al23+ O32-)
3. Multiply subscript and superscript for each ion then find the lowest whole number
ratio (Al2O3)
Name it!!! Aluminum Oxide
Examples: Zn2+ IZn2+ S2(More on p 223 practice problems)
Stock system of Nomenclature
Sometimes elements, usually transition metals, can form different cations. The stock
system was developed to show their different charges by using roman numerals
(Refer back to page 221)
Examples Cu (I) or Cu (II), Sn(II) or Sn(IV), V(II) or V(III) or even V(IV)
The same method is used as for binary ionic compounds
Cr3+ F- combines to form CrF3 and is called Chromium (III) Fluoride
Oxyanions and other polyatomic ions
Elements can bond together with different numbers of oxygen atoms (oxyanions)
If there are 2 possibilities: greater number of oxygen atoms ends with –ate,
smaller number of oxygen atoms ends with – ite.
If there are more possibilities use Hypo- for a prefix when there are less and
use Per- when there are more.
Examples: Sulfite or Sulfate
Nitrite or Nitrate
Hypochlorite, chlorite, chlorate, perchlorate
AgNO2 or AgNO3
Naming Binary Molecular Compounds
There are two systems the newer system is the stock system previously discussed.
The older system uses prefixes to denote how many atoms of an element are present.
General Rules:
Write the element with the lesser number of atoms first
Drop the last vowel of the prefix if the element starts with a vowel
Placing an –ide after the second element usually means there are 2
Acids and Salts
An acid refers to a water based solution that has unique properties.
Binary acids are composed of two elements (Hydrogen and something else)
Oxyacids consist of hydrogen, oxygen, and some other element(s)
If a hydrogen is lost from an acid an anion is usually produced
A salt is formed if the anion from an acid combines with a cation
 Resources
Modern Chemistry text (Holt, Rinehart, and Winston) Page 219 - 231