Comprehensive Study Guide for Oxidation States and Numbers

Fundamental Definitions of Oxidation States- Oxidation State (Number): Defined as the charge held by an element within a compound.- Variability of Oxidation States: Certain elements are capable of possessing multiple oxidation states. This variability occurs due to the nature of covalent bonding and the properties of transition metals.# Rules for Determining Oxidation States- Free Elements: The oxidation number for any free element is always $0$. This rule applies when there is only one element present and it possesses no charge.- Monatomic Ions: The oxidation state of any monatomic ion is represented by the specific charge given to that ion. This occurs when there is one element present with a defined charge.- Compounds: The total charge of any neutral compound is $0$. To satisfy this condition, all positive and negative charges must be balanced within the compound ($+ = -$).- Polyatomic Ions: The total oxidation state of a polyatomic ion is represented by the charge given to the ion. All individual oxidation states of the constituent elements must sum to equal the charge as written.# Specific Elemental Rules for Compounds and Polyatomic Ions- Alkali Metals: The oxidation number for Alkali Metals (Group 1) is always $+1$.- Silver: The oxidation number for silver ($Ag$) is always $+1$.- Alkaline Earth Metals: The oxidation number for Alkaline Earth Metals (Group 2) is always $+2$.- Zinc: The oxidation number for zinc ($Zn$) is always $+2$.- Hydrogen ($H$): The oxidation number of hydrogen is typically $+1$.- Exception for Hydrogen: When hydrogen acts as an anion, its oxidation number is $-1$.- Oxygen ($O$): The oxidation number of oxygen is typically $-2$.- Exception for Oxygen: When oxygen is part of a peroxide, its oxidation number is $-1$.- Caution regarding exceptions: The transcript explicitly states, \"DON’T GO LOOKING FOR EXCEPTIONS!\"- Halides: Halides have a $-1$ charge when they are not bonded with oxygen.- Sulfur ($S$): Sulfur has an oxidation number of $-2$ provided it is not bonded to oxygen.- Nitrogen ($N$) and Phosphorus ($P$): Both nitrogen and phosphorus have an oxidation state of $-3$ when they are not bonded to oxygen.# Calculus of Unknown Oxidation States- General Rule for Remaining Elements: For elements not covered by the specific predefined rules, use the known charges of accompanying elements to determine the unknown charge.- Algebraic Method: Set up an algebraic equation where the sum of oxidation numbers equals the total charge of the molecule or ion to solve for the remaining charge. This calculation can only be performed when there is only one unknown charge remaining.# Examples for Practice and Analysis- $S_2O_3$- $Na_2O_2$- $P_2O_5$- $NO_3^-$- $KClO_3$- $Cl_2$- $Ca(ClO_4)_2$- $Cl_2O$