مواضيع مميزة

Autoxidation The slow, flameless combustion of materials by reaction with oxy­gen; it is sometimes spelled autooxidation. Autoxidation is important because it is a useful reaction for converting compounds to oxygenated derivatives, and also because it occurs in situations where it is not desired (as in the destructive cracking of the rubber in automobile tires). Although virtually all types of organic …

Atomic mass : The mass of an atom or molecule on a scale where the mass of a carbon-12 (12C) atom is exactly 12.0. The mass of any atom is approximately equal to the total number of its protons and neutrons multiplied by the atomic mass unit, u = 1.6605397 x 10-24 gram. (Electrons are much lighter, about 0.0005486 u.) …

Amine A member of a group of organic compounds which can be considered as derived from ammonia by replacement of one or more hydrogens by organic radicals. Generally amines are bases of widely varying strengths, but a few which are actually acidic are known. Amines constitute one of the most important classes of organic compounds. The lone pair of electrons …

Aluminum A metallic chemical element, symbol Al, atomic number 13, atomic weight 26.98154, in group 13 of the periodic system. Pure aluminum is soft and lacks strength, but it can be alloyed with other elements to increase strength and impart a number of useful properties. Alloys of aluminum are light, strong, and readily formable by many metalworking processes; they can …

Alkene الألكينات و الألكاينات (الفصل 3 ) Alkenes and Alkynes Alkene One of the class of acyclic hydrocarbons containing one or more carbon-to­carbon double bonds. Alkenes (also called olefins) and alkynes (also called acetylenes) together constitute the family of organic compounds called unsaturated hydrocarbons, since they contain less than the number of hydrogens found in the corresponding saturated compound, alkane. …

Alkane A compound with the general formula CnH2n+2· Alkanes are open-chain (aliphatic or noncyclic) hydrocarbons with no multiple bonds or functional groups. They consist of tetrahedral carbon atoms, up to 105 carbons or more in length. The C-C bonds are formed from sp3 orbitals, and there is free rotation around the bond axis. Alkanes provide the parent names for all …

A coenzyme and one of the most impor­tant compounds in the metabolism of all organisms, since it serves as a coupling agent between different enzymatic reactions. Adenosine triphosphate is adenosine diphos­phate (ADP) with an additional phosphate group attached through a pyrophosphate linkage to the terminal phosphate group (see illustration). ATP is a powerful donor of phosphate groups to suitable acceptors …

The series of elements beginning with actinium (atomic number 89) and including thorium, protactinium, uranium, and the transuranium el­ements through the element lawrencium (atomic number 103). These elements have a strong chemical resemblance to the lanthanide, or rare-earth, elements of atomic numbers 57 to 71. Their atomic numbers, names, and chemical symbols are: 89, ac­tinium (Ac), the prototype element, sometimes …

التركيب الإلكتروني للعناصر (الكيمياء العامة المستوى الاول – الكلية الجامعية بالجموم)   التركيب الإلكتروني للعناصر عدد الكم الرئيسي (  n  ) تحديد الحجم النسبي للفلك و بعد الفلك عن النواة و طاقة الفلك و يأخذ القيم 3٫2٫1….. عدد الكم الثانوي (   L ) رقم يصف شكل الفلك الذي يوجد فيه الالكتـرون، و يأخــذ القيـــم العدديـــة ابتداء من الصفر إلى ( n-1 …

أشكال الطاقة (الكيمياء العامة المستوى الاول – الكلية الجامعية بالجموم) تعرف الطاقة بأنها القدرة على القيام بشغل أو نقل حرارة . تظهر الطاقة بعدة أشكال مثل الطاقة الضوئية ، الطاقة الصوتية ، الطاقة الحرارية ،  الطاقة الميكانيكية ، الطاقة الكيميائية و الطاقة الكهربائية . يمكن للطاقة أن تنتقل من شكل لآخر . قانون حفظ الطاقة بأنه لا يمكن للطاقة لأن …