In its outermost shell, and so it's very likely It really wants to get that extra electron to have eight valence electrons It's very easy to nabĪn electron off of it and then it has a positive charge, and it's made up of a chloride anion, so Cl minus. Positively-charged sodium cations, so you have an Na plus, so sodium is a group one element. We have talked about this in other videos. Table salt is sodium chloride, so sodium chloride.
Most common ionic compound in our daily life, and that is table salt. If the charges are the same, it's going to be a force of repulsion. And if we're talking about ions, r is going to be the distanceīetween their nuclei, and if the charges are different, it's going to be force of attraction. Maybe that's an ion, divided by r squared. To the product of the charges, so q one would be the charge of one of the charged particles. You may already be familiar with Coulomb's law, which is really the most important or underlying law behindĪll of what we know about electrostatics and how things with chargeĪttract or repulse each other, but a simplified version of Coulomb's law is just that the forceīetween charged particles, the magnitude of the force is going to be proportional And this is true is look up their values: magnesium fluoride is 2922 kJ/mol while sodium chloride is only 786 kJ/mol. With both of these factors in mind, we should assume that magnesium fluoride has a greater lattice energy compared to sodium chloride. 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.
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