Sodium and magnesium have about the same atomic radii (102 pm and 72 pm respectively), with the main difference being because of the fluoride and chloride ions (133 pm and 181 pm respectively). So magnesium fluoride also has a smaller distance between the ions which also results in greater attraction between the ions and generates a greater lattice energy compared to sodium chloride. The distance between a magnesium and fluoride ion is 205 pm, while the distance between a sodium and chloride ion is 283 pm. We can be thorough and also consider the atomic radii of all the ions concerned too. So the product the magnesium fluoride's charges is 2 while the sodium chloride's charge product is only 1. This is because the magnesium ion has a +2 charge (and the fluoride has a -1 charge), while the sodium and chloride ions have +1 and -1 charges respectively. If we consider magnesium fluoride (MgF2) and sodium chloride (NaCl), then we would assume that magnesium fluoride would have a greater lattice energy. This means we can usually assume that ions with greater magnitude charges will result in greater lattice energies, and without having to take into consideration the atomic radii. Generally the charges of the ions have more bearing than the distance between them when determining lattice energies. If the goal is to maximize the lattice energy then you'd want ions with larger magnitude charges and/or small in size ions. So both the magnitude of the ion's charges and their atomic radii effect the lattice energy. And the denominator consists of of the distance between the two ions, squared. ![]() If we observe the equation of Coulomb's Law the numerator consists of the product of the absolute value of the charges of the ions. So lattice energy is measuring how attracted both the ions are to each other in an ionic compound. In ionic compounds the force is always attractive since the ions have different charges. Whether the force is attractive or repulsive depends on whether the charges have the same sign or not. ![]() Coulomb's Law describes the force of attraction (or repulsion) between two point charges. Lattice energies of ionic compounds broadly correspond with Coulomb's Law which Sal provided in the video.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |