1.3-2 Covalently Bonded Solids
Covalent bonds arise by electron sharing. Many predominantly covalently bonded ceramics, especially Si-based ones, such as SiC, Si3N4, and silicates, are composed of Si atoms simultaneously bonded to four other atoms in a tetrahedral arrangement. Ground state configuration of Si has the valence electron in 3s23p2 configuration, as shown in Figure 1.9 a. It shows that Si can have two primary bonds when it combines with another element atom, because Si atom has two unpaired electrons.
In reality, there are four primary bonds associated with each Si atom. This can happen by hybridization between s and p wave functions. The s orbital hybridizes with all the three p orbitals to form sp3 hybrid orbitals (Figure 1.9b). Hybrid orbitals possess both s and p character, and directionally reaches out in space as lobes in a tetrahedral arrangement with a bond angle of 109° (Figure 1.9c). Each orbital is populated by one electron (Figure 1.9b). Now, each Si can bond to four other Si atoms or any other four atoms to give three-dimensional structures.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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