Which of the following compounds would have the highest melting point?
a. CsF
b. LiF
c. NaBr
d. LiCl
e. NaCl
LiF
To determine which of the compounds has the highest melting point, we need to consider the properties of the compounds.
The melting point of a compound is influenced by its ionic bond strength, which is determined by the charges and sizes of the ions involved. Generally, compounds that have stronger ionic bonds tend to have higher melting points.
Let's analyze the compounds:
a. CsF - Cesium fluoride: Cs+ and F- ions. Cesium (Cs) is a larger cation compared to the other cations in the options, and fluoride (F-) is a small anion. Larger cations and smaller anions usually have stronger ionic bonds.
b. LiF - Lithium fluoride: Li+ and F- ions. Lithium (Li) is a smaller cation compared to cesium, and fluoride is the same anion as in CsF.
c. NaBr - Sodium bromide: Na+ and Br- ions. Sodium (Na) is larger compared to lithium, and bromine (Br-) is a larger anion compared to fluoride.
d. LiCl - Lithium chloride: Li+ and Cl- ions. Lithium is the same cation as in LiF, and chlorine (Cl-) is a larger anion compared to fluoride.
e. NaCl - Sodium chloride: Na+ and Cl- ions. Sodium is the same cation as in NaBr, and chlorine is the same anion as in LiCl.
Based on the size and ionic charges of the ions, the compound with the highest melting point would be the one with the strongest ionic bond. In this case, CsF would have the highest melting point due to the combination of the large cesium cation and the small fluoride anion, which leads to a strong ionic bond.
So the answer is: a. CsF
To determine which compound would have the highest melting point among the given options, we need to consider the types of bonds present in each compound and the strength of those bonds.
The given options are all ionic compounds composed of a metal cation (Cs, Li, Na) and a nonmetal anion (F, Br, Cl). Ionic compounds are held together by strong electrostatic forces of attraction between the positive and negative ions.
In general, the strength of the ionic bond depends on two factors: the charge of the ions and their size. Higher charge and smaller ion size generally result in stronger bonds.
Let's analyze the options one by one:
a. CsF: Cesium (Cs) is a larger atom compared to lithium (Li) and sodium (Na) and therefore has weaker bonding. Fluorine (F) is a smaller atom compared to bromine (Br) and chlorine (Cl) and therefore has stronger bonding. However, since CsF has both larger cations and smaller anions compared to the other options, it is difficult to determine if its melting point is the highest.
b. LiF: Lithium (Li) has a smaller size compared to sodium (Na) and cesium (Cs), resulting in stronger bonding. Fluorine (F) is the same for all options. Therefore, LiF has a relatively higher melting point compared to the other options.
c. NaBr: Sodium (Na) has a larger size compared to lithium (Li) and cesium (Cs), resulting in weaker bonding. Bromine (Br) is larger compared to fluorine (F) but smaller compared to chlorine (Cl). Therefore, NaBr has a relatively lower melting point compared to LiF but higher compared to options with cesium (Cs).
d. LiCl: Lithium (Li) has a smaller size compared to sodium (Na) and cesium (Cs), resulting in stronger bonding. Chlorine (Cl) is larger compared to fluorine (F) but smaller compared to bromine (Br). Therefore, LiCl has a relatively higher melting point compared to NaBr but lower compared to LiF.
e. NaCl: Sodium (Na) has a larger size compared to lithium (Li) and cesium (Cs), resulting in weaker bonding. Chlorine (Cl) is larger compared to fluorine (F) but smaller compared to bromine (Br). Therefore, NaCl has a relatively lower melting point compared to LiF but higher compared to compounds with cesium (Cs).
Based on this analysis, LiF would have the highest melting point among the given options.