ACCTG418 Chapter Notes -Molar Mass, Electronegativity, Chemical Polarity
6 Mar 2014
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Forces that hold molecules together in the condensed phases. Look at the relative forces for the 2 molecules. Ions in mgo have charges of 2 whereas ions in nacl have charges of 1. Ion is attracted by several other ions with opposite charge. Electrostatic attraction (opposite charges) (f is positive b/c q2 is negative) F = k q1 q2 r2 k = constant q1, q2 charges separated by a distance r. Stronger force more energy to break intermolecular forces holding molecules together higher melting point (boiling point) Ionic radii effect based on ionic radii trends (unit 1) r = rcation + ranion rna+ (99 pm) > rmg2+ (72 pm) rcl (181 pm) > ro2 (140 pm) You are expected to know the trends, not actual values for the radii. So r is smaller in mgo leading to a stronger forces. Overall, both effects contribute to stronger forces in. Attraction between the charge of the ion and an opposite dipole.
