أكاديميا - كولنز - معاجم الجيب العلمية - الكيمياء - انكليزي - فرنسي - عربي الحرف ١_ r

Academia - Collins - Pocket Scientific Dictionaries - Chemistry - English - French - Arabic Letter 1_ R


radical
radical m

Root referring to inorganic chemistry. A radical is an atom or a group of atoms present in a compound that is responsible for the distinctive properties of that compound, for example:

Sulfate4/-SO2-
Carbonate CO2-/3-
Hydroxide -OH2-


radioactivity
radioactivity f

Radioactivity. The spontaneous disintegration of the atomic nucleus accompanied by the release of electromagnetic radiation (gamma (y) rays) or particles (alpha or beta B particles).

Not all elements have radioactive isotopes, although many radioactive isotopes can now be created artificially.
Some radioactivity occurs naturally, such as in the state of isotopes within rocks. Granite usually has a relatively high concentration. Living bodies contain radioactive carbon that can be used to determine the age of the remains of these bodies.
(See radiocarbon dating). Types of emissions that accompany the decay of radioactivity include electrons (beta particles).
Alpha particles.
Gamma rays.
See half-life and nuclear reactions.


radiocarbon dating
Dation f par radiocarbone

Radiocarbon dating. Carbon-14 (14C) is a naturally occurring radioactive isotope. All living bodies contain a substance that is maintained at a constant level through continuous exchange through nutrition and respiration. This exchange stops at death, and the 14C level falls at a constant rate as a result of the decay of radioactivity. Scientists measure the amount of radioactivity remaining in the remains, which enables them to...
Knowing the age of the remains.

rate of reaction
vitese for reaction

Reaction rate. The rate (or speed) at which the reaction takes place depends on several factors:

Temperature: The higher the temperature, the faster the reaction because the particles move with greater energy.

Particle size: The smaller the reacting particle, the greater the surface area on which the reaction takes place and the faster the reaction.

Concentration: As the concentration of the solution increases (or the pressure of the gas increases), the reaction accelerates. This results from there being more particles to react within a given volume.

Catalysts: These substances change the reaction rate by providing an alternative reaction pathway in which the reaction can take place.


rayon
rayon m

Artificial silk. Rayon. One of the first fibers created by man. It consists of cellulose (from wood). Wood contains cellulose fibers but they are too short to be spun into yarn. Therefore, cellulose is dissolved in a sodium hydroxide/carbon disulfide solution and then sprayed with dilute sulfuric acid. Here the cellulose is reshaped into long threads ready for knitting. Artificial silk is used to make clothes and curtains.


reaction. reaction
reaction f

interaction. When a chemical reaction occurs, a new substance is formed that has properties different from the properties of the reactants. Reactions can be accompanied by heat, light, sound, or color change.


reactivity series
Series f reactive

Interactive String A string of elements arranged by
Its chemical reactivity, example:

potassium
sodium
Calcium
Magnesium
Aluminium
zinc
Iron
bullets
copper
silver

This series is a short series with only a few elements, but the same conclusions apply more broadly:

Oxides are returned with elements above them, not the other way around:

Mg + CuO → MgO + Cu
(steel) (steel) (steel) (steel)

No reaction - (solid) Mgo + (solid) Cu
No reaction - (solid) ZnO + (solid) Cu

Mineral ions are traced back to elements above them, not the other way around:

Zn + 2Ag+ → Zn2+ + 2Ag
(solid) (aqueous) (aqueous) (solid)

No reaction - (aqueous) Zn2 + (solid) Ag

The further up the chain one moves, the stronger the interaction with water or acids becomes. Potassium reacts violently with cold water, while magnesium reacts very slowly with cold water and strongly with steam. Copper does not react with either of the two.

See electrochemical. It is a special series Non-metals.