Just as bonds can be polar, molecules can also be polar • Molecular polarity plays major role in: – solubility (like dissolves like), – reactivity (biochemical interactions) The weaker attractions are called secondary bonds or intermolecular forces. 2. DSE 1 Polymer Chemistry Semester V!! %%EOF A polymer (/ ˈ p ɒ l ɪ m ər /; Greek poly-, "many" + -mer, "part") is a substance or material consisting of very large molecules, or macromolecules, composed of many repeating subunits. CHEMICAL BONDING AND MOLECULAR STRUCTURE 101 4.1 KÖSSEL-LEWIS APPROACH TO CHEMICAL BONDING In order to explain the for mation of chemical bond in terms of electrons, a number of attempts were made, but it was only in 1916 when Kössel and Lewis succeeded independently in giving a satisfactory explanation. Solution A chemical bond is the force of attraction that holds various constituents (atoms or ions) together in different chemical species. Polymers; Chemical Bonds; Physical Bond; Ionic Bond; Covalent Bond . Chemical Bonding and Polymer Structure . Since molecular forces are relatively short range, close contact and good wetting conditions are required. 121 0 obj <>stream 0000003046 00000 n Larger molecules generally are more polarizable, so large polymers with high molecular weights can have significant dispersion forces. (Monomers). Ultra high molecular weight polyethylene (UHMWPE), which has a molecular weight in excess of 3,000,000 g/mole, is used to make bulletproof vests. MCQs on Chemical Bonding and Molecular Structure for NEET. vc`�^�3 .8` The types of bonding forces vary in their strength as measured by average bond energy. Induction forces are weak and temperature independent. Free PDF download of NCERT Solutions for Class 11 Chemistry Chapter 4 Chemical Bonding and Molecular Structure solved by Expert Teachers as per NCERT (CBSE) Book guidelines. It is clear that adhesion needs molecular bonding. Understanding the evolution of macroscopic adhesion based on fundamental molecular interactions is crucial to designing strong and smart polymer/metal interfaces that play an important role in many industrial and biomedical applications. endstream endobj startxref The elements found most frequently in polymers and their valence numbers are: H, F, Cl, Bf, and I with 1 valence electron; O and S with 2 valence electrons; n with 3 valence electrons and C and Si with 4 valence electrons. "� �E���&���!�킄��p�������splfFw}rrBguY7�&[J���b�t_��>��gu�L��Y�5�YYԕc]�Ʊ���h4�ϊ��l%gF�)����+��0\ Except for noble gases, no other elements occur independently. trailer 9-2 Theories of Chemical Bonding Chapter 9 9.1 Introduction to Bonding Theories OWL Opening Exploration 9.X As you learned in the previous chapter (Section 8.1), chemical bonds form when two atoms approach each other and the attractive forces are greater than the repulsive forces (Figure 9.1). A hydrogen bond is the attraction between the lone pair of an electronegative atom and a hydrogen atom that is bonded to an electronegative atom, usually nitrogen, oxygen, or fluorine. • Secondary bonding forces arise from atomic or molecular … 0000001473 00000 n The term polymer is defined as very large molecules having high molecular mass. In Polymers, strong covalent bonds join atoms to each other in individual polymer molecules. 504 0 obj<>stream The revision notes help you revise the whole chapter in minutes. Circles designate individual mer units. Bond and Molecular Polarity Polar bonds result from unequal sharing of electrons – Due to electronegativity differences – Produced bond dipoles.Produced bond dipoles. The attractive force by which atoms, ions and molecules are held together is known as a chemical bond. 502 16 Chemical bonding and molecular structure grade 11 1. 0000000016 00000 n Polymers structures At lower molecular weight, the polymer chains are loosely bonded by weak van der Waals forces and the chains can move easily, responsible for low strength,althoughcrystallinityispresent.Incaseoflargemolecularweight $����? Ex: Starch, Polyvinyl chloride, Polyethylene, Nylon 6, 6 and etc. 0000029595 00000 n Dispersion forces depend on the polarizability of a molecule. Free PDF download of Class 11 Chemistry revision notes & short key-notes for Chapter 4 - Chemical Bonding and Molecular Structure to score high marks in exams, prepared by expert Chemistry teachers from latest edition of CBSE(NCERT) books. 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