Chemistry

From Wikipedia, the free encyclopedia.

Chemistry is the study of the atomic building blocks of nature, how they combine and their combinations which form the solids, liquids, and gases that make up most forms of matter. For the many different chemical elements and compounds, see:

• The Periodic table
• List of compounds
• Inorganic chemistry, including solid state chemistry, which studies the basic principles that are applied in mineralogy and materials science.
• Organic chemistry, which underlies biochemistry and polymer chemistry and is the study of carbon-containing molecules.
• Physical chemistry, which includes computational chemistry, quantum chemistry and surface chemistry.
• Analytical chemistry, the basis of environmental chemistry.
• Photochemistry, which through photosynthesis drives all of life.

Basics

Atomic theory is basic to Chemistry. The theory states that all matter is composed of a set of very small units called atoms. One of the very first laws to be discovered leading to the establishment of Chemistry as a science is the Law of Conservation of Matter. The law states there is no detectable change in the quantity of matter during an ordinary chemical reaction. (Modern Physics now teaches that atoms and energy can be neither created nor destroyed.) On a superficial level this means that if we start off with 10,001 atoms and proceed with many chemical reactions, we will be left with 10,001 atoms. Even if we started off with something green and gooey and ended up with something black and hard there will still be the same number of atoms. The mass will be the same too if the energy gained or lost is accounted for. Chemistry studies the interactions of these atoms, sometimes alone but more often combined with (bonded to) other atoms to form ions and molecules. These atoms interact with other atoms (e.g. a wood fire is the combination of oxygen atoms from the air with the carbon and hydrogen atoms in the wood) and they also interact with light (a photograph is formed from the changes that light causes to the chemicals on a film) and other types of radiation. One surprisingly early finding was that these atoms almost always combine in definite ratios or proportions: silica sand is a structure where the ratio of silicon atoms to oxygen atoms is 1:2. We now know that there are exceptions to this Law of Definite Proportions (integrated circuits are a good example). Another key discovery in chemistry was that when a change is made, the amount of energy gained or lost will always be the same. This leads to the important concepts of equilibrium, thermodynamics, and kinetics. The most interesting theory describing all of chemistry is Quantum Mechanics. This theory is complex, non-intuitive, and difficult to master. Often, simpler concepts are used to predict the results of experiments. These concepts (e.g. acid/base chemistry) are limited in scope, but much easier to understand and apply. College students typically study chemistry in the following "blocks": Analytical Chemistry, Physical Chemistry, Organic Chemistry, Inorganic Chemistry, Polymer Chemistry and Biochemistry. Often, discoveries in chemistry are made by physicists, biologists, chemical engineers or pharmacists.

• Scientific method
• SI base unit
• Significant figures
• The Atom
• Orbitals
• Periodic Table of Chemical elements
• Isomerism
• Allotropes
• Isotopes
• Ion
• Electron configuration
• Periodic Trends
  • Electronegativity
  • Atomic radius, Ionic radius
  • Ionization energy
  • Electron affinity
• Elemental Groups: S-block, D-block, F-block, P-block

Chemicals and Interactions

• Systematic names
• Chemical formula
  • Empirical formula
  • Molecular formula
• Chemical bonding
• Chemical polarity
• Chemical equation
• Chemical reaction
• Colors of chemicals

Quantitative Chemistry

• The mole
• Stoichiometry
• Thermochemistry
• Hess's Law
• Calorimetry

States of Matter

• Kinetic theory of gases
• Ideal gas
• Condensed matter physics
• Solutions
• Concentration of solutions
• Colligative properties
• Chemical equilibrium
• Le Chatelier's principle
• Solubility
• Precipitates
• Common-ion effect

Acids and Bases

• Acid-base reaction theories
• Strong acids
• Weak acids
• pH and the strength of acids
• Systematic naming of acids and bases
• Self-ionization of water
• Buffers
• Acid-Base titration
• Redox reactions
• Electrochemistry

Kinetics and Thermodynamics

• Chemical kinetics
• Reaction rates
• Spontaneous processes
• Enthalpy
• Entropy
• Gibbs free energy
• Nuclear chemistry
• Biochemistry

History of Chemistry

• Alchemy
• Discovery of the chemical elements
• Timeline of chemical element discovery
• Nobel Prize in Chemistry

See also

• Chemistry basic topics
• Chemist and List of chemists
• American Chemical society
• International Union of Pure and Applied Chemistry
• Chemical engineering

External links

• IUPAC Nomenclature Home Page, see especially the "Gold Book" containing definitions of standard chemical terms
• Material safety data sheets for a variety of chemicals