Periodic Table History and Chemical Bonding Basics
History of the Periodic Table
The classification of elements began in the nineteenth century following their gradual discovery. Initially, the distinction was simply between metals and nonmetals.
- Johan Döbereiner (1817): Introduced the concept of Triads.
- John Newlands (1863): Proposed the Law of Octaves, sorting elements according to mass.
- Lothar Meyer (1869): Sorted elements based on atomic volume.
- Dmitri Mendeleev (1869): Sorted elements based on mass and properties, leaving gaps for undiscovered
Free Energy and Reaction Types: Thermodynamics Explained
Free Energy and Types of Reactions
We can consider four types of reactions:
-
Exothermic Reactions (ΔH < 0) with increasing disorder (ΔS > 0) for example:
2H2O(l) -> 2H2(g) + O2(g)
The terms ΔH and -TΔS are both negative, so that ΔG is always negative at all temperatures. Consequently, these reactions are always spontaneous. -
Endothermic Reactions (ΔH > 0) with increasing disorder (ΔS > 0) for example:
SO3(g) -> SO2(g) + 1/2 O2(g)
The spontaneity of these reactions is favored
Acid-Base Chemistry: Concepts, Calculations, and Equilibrium
CATION | ANION | SOLUTION WILL BE |
ACIDIC | NEUTRAL | ACIDIC |
NEUTRAL | NEUTRAL | NEUTRAL |
NEUTRAL | BASIC | BASIC |
ACIDIC | BASIC | Ka > Kb ACIDIC |
Ka = Kb NEUTRAL | ||
Ka < Kb BASIC |
Ka = ([H+] x [B–]) / [HB]
Measure known amount of the weak acid, HB
Determine [H+]eq by measuring pH if necessary
Use the balanced equation to find [B–]eq
Calculate [HB]eq which is [HB]o – [H+]eq
Solve for Ka
Larger Ka value = the stronger the weak acid
Smaller pKa value = the stronger the weak acid
Weak Acids:
Ionizable hydrogen atom
Anions with an ionizable hydrogen
Chemical Nomenclature: Formulas, Oxidation States & Naming
Chemical Nomenclature Fundamentals
Oxidation States and Acid Naming Conventions
The name of an oxyacid depends on the oxidation state of the central non-metal atom (X). Prefixes (hypo-, per-) and suffixes (-ous, -ic) are used as follows:
| Oxidation State | Prefix | Suffix | Example (Cl) | Formula (Cl) | Example (S) | Formula (S) |
|---|---|---|---|---|---|---|
| Low (+1, +2) | hypo- | -ous | Hypochlorous acid | HClO | N/A | N/A |
| Intermediate (+3, +4) | (none) | -ous | Chlorous acid | HClO2 | Sulfurous acid | H2SO3 |
| High (+5, +6) | (none) | -ic | Chloric acid | HClO3 | Sulfuric acid | H2SO4 |
| Highest (+7) | per- | -ic | Perchloric |
Genetics, Thermodynamics, and Chemical Reactions Explained
Genetics and Heredity
Genotype: The complete set of genes an individual inherits from their parents.
Phenotype: The observable characteristics of an organism, resulting from the interaction of its genotype with the environment.
Alleles and Inheritance
Homozygous: An individual possessing two identical alleles for a specific trait.
Heterozygous: An individual possessing two different alleles for a specific trait.
Gene: A unit of heredity containing genetic information, located on chromosomes in a linear
Read MoreChemical Kinetics, Surface Phenomena, and Material Properties
Pseudo First Order Reactions
The order of a reaction is sometimes altered by conditions. Consider a chemical reaction between two substances when one reactant is present in large excess. For example, during the hydrolysis of 0.01 mol of ethyl acetate with 10 mol of water, the amounts of the various constituents at the beginning (t = 0) and completion (t) illustrate this phenomenon, known as a pseudo-first-order reaction.
Collision Theory of Chemical Reactions
Although the Arrhenius equation is applicable
Read More