أرشيف يوم: 28/11/2018

Aufbau Principle

A principle that governs the order in which the atomic orbitals are filled in elements of successive proton number; i.e. a statement of the order of increasing energy. The order is as follows: 1s², 2s², 2p⁶, 3s², 3p6, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5p⁶, 6s², 4f¹⁴, 5d¹⁰, 6p⁶, 7s², 5f¹⁴, 6d¹⁰ (the superscript indicates the maximum number of …

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مجهر القوة الذرية

أداة تستخدم لفحص الأسطح. يتم وضع مجس صغير يحتوي على رقيقة صغيرة جدا من الألماس فوق سطح العينة بواسطة ناتئ محمّل بنابض. عند تحريك المجس ببطء على السطح ، يتم قياس القوة بين السطح والطرف ويتم رفع المجس تلقائيًا وخفضه للحفاظ على ثبات هذه القوة. يتيح مسح السطح بهذه الطريقة …

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Atomic force microscope AFM

An instrument used to investigate surfaces. A small probe consisting of a very small chip of diamond is held just above a surface of a sample by a spring-loaded cantilever. As the probe is slowly moved over the surface the force between the surface and the tip is measured and the probe is automatically raised and lowered to …

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Aromatic compound

An organic compound containing benzene rings in its structure. Aromatic compounds, such as benzene, have a planar ring of atoms linked by alternate single and double bonds. The characteristic of aromatic compounds is that their chemical properties are not those expected for an unsaturated compound; they tend to undergo nucleophilic …

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Arrhenius equation

An equation relating the rate constant of a  chemical reaction and the temperature at which the reaction is taking place: k = Aexp(–Ea/RT) where A is a constant, k the rate constant, T the thermodynamic temperature in kelvins, R the gas constant, and Ea the activation energy of the reaction. Reactions proceed at different rates at different temperatures, …

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Antimony trioxide

Antimony trioxide with the formula Sb₂O₃, molecula weight 291.518 g/mol , density 5.2 g/cm3 , melting point 656 °C .  Antimony trioxide is a white insoluble solid. It is an amphoteric oxide with a strong tendency to act as a base. It can be prepared by direct oxidation by air, oxygen, or steam and is formed when antimony(III) chloride is hydrolyzed by …

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