Bonding attractive forces

Intermolecular bonds Attractive forces which act between molecules, for example van der Waals forces. 

Ionic bonds Attractive forces between oppositely charged groups in aqueous solutions. 20 0.25 Depending on the polarity of the interacting charged species and related to Mj/Dr ir... 

Chemical bonds Attractive forces that hold atoms together in elements and compounds. 

Molecular solids made up of polar molecules form crystals that are a little harder and melt at temperatures a little higher because of the additional dipole-dipole or hydrogen bonding attractive forces. Examples are ice, sucrose (table sugar), and naphthalene (moth balls). The crystals of these solids are not very rigid and can be crushed rather easily. You can hear the crystals of sugar spilled on the kitchen floor crushing underfoot. Molecular solids do not conduct electricity. 

Hydrogen bond Attractive forces hold the protein in a specific shape. 

The virial equation is appropriate for describing deviations from ideality in those systems where moderate attractive forces yield fugacity coefficients not far removed from unity. The systems shown in Figures 2, 3, and 4 are of this type. However, in systems containing carboxylic acids, there prevails an entirely different physical situation since two acid molecules tend to form a pair of stable hydrogen bonds, large negative... 

The attractive force is called hydrogen bonding and is normally represented by a dotted line, for example A—H A—H it is this... 

Atoms combine with one another to give compounds having properties different from the atoms they contain The attractive force between atoms m a compound is a chemical bond One type of chemical bond called an ionic bond, is the force of attraction between oppositely charged species (ions) (Figure 1 4) Ions that are positively charged are referred to as cations, those that are negatively charged are anions... 

Were we to simply add the ionization energy of sodium (496 kJ/mol) and the electron affin ity of chlorine (—349 kJ/mol) we would conclude that the overall process is endothermic with AH° = +147 kJ/mol The energy liberated by adding an electron to chlorine is msuf ficient to override the energy required to remove an electron from sodium This analysis however fails to consider the force of attraction between the oppositely charged ions Na" and Cl which exceeds 500 kJ/mol and is more than sufficient to make the overall process exothermic Attractive forces between oppositely charged particles are termed electrostatic, or coulombic, attractions and are what we mean by an ionic bond between two atoms... 

The H—O—H angle m water (105°) and the H—N—H angles m ammonia (107°) are slightly smaller than the tetrahedral angle These bond angle contractions are easily accommodated by VSEPR by reasoning that electron pairs m bonds take up less space than an unshared pair The electron pair m a covalent bond feels the attractive force of... 

The characteristic feature of valence bond theory is that it pictures a covalent bond between two atoms in terms of an m phase overlap of a half filled orbital of one atom with a half filled orbital of the other illustrated for the case of H2 m Figure 2 3 Two hydrogen atoms each containing an electron m a Is orbital combine so that their orbitals overlap to give a new orbital associated with both of them In phase orbital overlap (con structive interference) increases the probability of finding an electron m the region between the two nuclei where it feels the attractive force of both of them... 

Relatively simple notions of attractive forces between opposite charges are suffi cient to account for many of the properties of chemical substances You will find it help ful to keep the polarity of carbon-oxygen and carbon-halogen bonds m mind as we develop the properties of alcohols and alkyl halides m later sections... 

Dipole/mduced dipole and dipole-dipole attractive forces make alcohols higher boiling than alkanes of similar molecular weight The attractive force between —OH groups is called hydrogen bonding... 

As shown m Figure 16 1 however the presence of an oxygen atom permits ethers to participate m hydrogen bonds to water molecules These attractive forces cause ethers to dissolve m water to approximately the same extent as comparably constituted alco hols Alkanes cannot engage m hydrogen bonding to water... 

In general aldehydes and ketones have higher boiling points than alkenes because they are more polar and the dipole-dipole attractive forces between molecules are stronger But they have lower boiling points than alcohols because unlike alcohols two carbonyl groups can t form hydrogen bonds to each other... 

Critical micelle concentration (Section 19 5) Concentration above which substances such as salts of fatty acids aggre gate to form micelles in aqueous solution Crown ether (Section 16 4) A cyclic polyether that via lon-dipole attractive forces forms stable complexes with metal 10ns Such complexes along with their accompany mg anion are soluble in nonpolar solvents C terminus (Section 27 7) The amino acid at the end of a pep tide or protein chain that has its carboxyl group intact—that IS in which the carboxyl group is not part of a peptide bond Cumulated diene (Section 10 5) Diene of the type C=C=C in which a single carbon atom participates in double bonds with two others... 

The AMBER force field replaces the van der Waals by a 10-12 potential for pairs of atoms that can participate in hydrogen bonding (equation 12). The hydrogen bond potential does not contribute significantly to the hydrogen bonding attraction between two atoms rather, it is implemented to fine-tune the distances between these atoms. 

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