Hydrogen bond electronegative atom

Two hydrogen-bonded electronegative atoms can approach each other more closely than the sum of their molecular radii. In other words, the intermolecular distance between B. .. H is less than the value expected from summing the two van der Waals radii of... 

The water molecule appears to behave in some crystals very much as it does in ice (p. 232), attaching itself to other molecules by approximately tetrahedrally disposed hydrogen bonds provided atoms of sufficiently high electronegativity are present (Fig. 108). It is attached to F or O atoms in various ways (Fig. 109) (b) shows the one employed in crystalline CUSO4.5H2O. In some instances the water molecule is attached directly to both anion and cation (Fig. 110). 

Hydrogen bonding is a relatively strong dipole-dipole force that acts between a polar bond containing a hydrogen atom and the bonded electronegative atoms, N,... 

The direction of the dipole moment is toward the more electronegative atom In the listed examples hydrogen and carbon are the positive ends of the dipoles Carbon is the negative end of the dipole associated with the C—H bond... 

Hence, exists only when hydrogen is bonded to the most electronegative atoms. In aqueous solutions, hydrates to form H O" ion. 

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