Fundamental Chemistry Terms and Definitions
Atomic Mass Unit (amu)
A unit of mass used to express atomic and molecular weights, equal to one-twelfth of the mass of an atom of carbon-12.
Ion
An atom or group of atoms that carries an electric charge.
Mole
The SI unit for the amount of substance, containing approximately 6.022 x 1023 elementary entities (atoms, molecules, ions, etc.).
Molecule
A group of two or more atoms held together by chemical bonds.
Atomic Mass
The mass of an atom, typically expressed in atomic mass units (amu). It is approximately
Read MoreFundamental Chemistry Concepts: Atoms and Bonds
Subatomic Particles Discovery
Electron
Electrons allow electric current conduction in discharge tubes. Discovered by J.J. Thomson (1897), cathode ray particles were identified as negatively charged and possessing very little mass.
Proton
Observed in discharge tubes as rays traveling opposite to cathode rays when using a perforated cathode (canal rays). Discovered by E. Goldstein (1886), canal rays were found to consist of particles with a positive electric charge and a mass approximately 1837 times
Read MorePeriodic 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 |