Intermolecular Forces of Attraction PDF

Intermolecular Forces (IMF) John Alfred J. Lobaton Discussant  What will happen to a liquid when it boils? Why does it take so long to boil?  , often abbreviated to IMF, are the attractive forces that arise between the positive components (or proto...

Intermolecular Forces (IMF) John Alfred J. Lobaton Discussant  What will happen to a liquid when it boils? Why does it take so long to boil?  , often abbreviated to IMF, are the attractive forces that arise between the positive components (or protons) of one molecule and the negative components (or electrons) of another molecule.  The boiling point of a substance is proportional to the strength of its intermolecular forces - the stronger the intermolecular forces, the higher the boiling point.  By comparing the boiling points of different substances, we can compare the strengths of their intermolecular forces. This is because the heat absorbed by the substance at its boiling point is used to break these intermolecular forces and to convert the liquid into vapor. Types of Intermolecular Forces (IMF) of attraction:  1. Dipole-dipole forces exist between molecules that are polar- those that have a permanent dipole moment due to uneven sharing of electrons.  There is an uneven sharing of electrons due to difference in electronegativity. The higher electronegativity the element is the stronger its pull.  Electronegativity - is a chemical property that describes an atom’s ability to attract electrons toward itself. What element in the periodic table has the highest and lowest electronegativity? Fluorine and Francium Why is it the shape of water molecule bent and not straight?  When can we say that the molecule is polar? A molecule is polar if it has a dipole, where one side of the molecule has a positive charge, and the other side has a negative charge. This results from an uneven distribution of electrons typically from a polar-covalent or ionic bond. When can we say that the molecule is polar?  - is the intermolecular forces of attraction between a charge ion (cation or anion) and a molecule with a partial charge called dipole. These interactions are always attractive, and are most common in solutions where ionic compounds dissolve in polar liquids. One basic example is NaCl dissolved in H2O. HOW?  When salt (NaCl) is dissolved in water (H 2 O), Na and Cl components are separated to each other. Na, with a positive charge will attract the negative end of water which is the oxygen (O). Similarly, Cl, with a negative charge will attract the other end of water w/c is the hydrogen (H).  Why does a dipole molecule bonds with a charge ion? Why does it never been contented? Are they a cheater?  It is sometimes called dipole- induced dipole interactions. - is the weakest intermolecular force. It is a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles.  In temporary dipole, the atom becomes distorted (or changed in shape) because of the movement of electrons. When that happens, there comes a more concentrated side of a molecule making it denser, thus it becomes partially negative. The other side becomes less concentrated making it less dense, thus it becomes partial negative.  When a temporary dipole turns into an induced dipole, it will be attracted or will attract nearby atoms. That nearby atom becomes a dipole when its electrons becomes concentrated on one side making it partially negative, and the other side is partially positive because it has less concentrations of electrons.  - is a special type of dipole-dipole attraction between molecules, not a covalent bond to a hydrogen atom. Examples of Hydrogen bonding: