Question

MgO melts at a much higher temperature (2,852°C) than NaF (993°C). What is the primary reason for this significant difference in melting points? Option 1: MgO has a lower density than NaF. Option 2: NaF has a more complex crystal structure. Option 3: MgO exhibits ionic bonding, whereas NaF exhibits covalent bonding. Option 4: NaF molecules are larger in size than MgO molecules.

Answer 1

The primary reason for the difference in melting points between MgO and NaF is that MgO exhibits ionic bonding, whereas NaF exhibits covalent bonding.

Step-by-step explanation:

The primary reason for the significant difference in melting points between MgO and NaF is that MgO exhibits ionic bonding, whereas NaF exhibits covalent bonding. Ionic bonds are formed between a metal and a nonmetal, while covalent bonds are formed between two nonmetals. In ionic bonding, the metal donates electrons to the nonmetal, creating charged ions that are attracted to each other by electrostatic forces. This creates strong bonds that require more energy to break, resulting in a higher melting point. On the other hand, covalent bonds involve the sharing of electrons between atoms, creating weaker bonds that require less energy to break, resulting in a lower melting point.

Answer 2

Option 3 is the correct choice. The difference in bonding type (ionic vs. covalent) and the associated bond strength is the primary reason for the significant difference in melting points between MgO and NaF.

The primary reason for the significant difference in melting points between MgO and NaF is their difference in bonding type and strength. Let's break down each option step by step:

Option 1: MgO has a lower density than NaF.

- Density alone is not the primary factor determining melting points. Melting points are primarily determined by the strength and type of chemical bonds between atoms or ions in a substance.

Option 2: NaF has a more complex crystal structure.

- The complexity of the crystal structure can influence melting points to some extent, but it is not the primary reason for the significant difference in melting points between MgO and NaF.

Option 3: MgO exhibits ionic bonding, whereas NaF exhibits covalent bonding.

- This is the correct answer. Ionic bonds are typically stronger than covalent bonds, and this difference in bond strength directly affects the melting points of compounds. In MgO, there are strong ionic bonds between magnesium (Mg²⁺) and oxygen (O²⁻) ions, whereas in NaF, there are covalent bonds between sodium (Na⁺) and fluorine (F⁻) atoms. Ionic bonds tend to require more energy to break, leading to higher melting points.

Option 4: NaF molecules are larger in size than MgO molecules.

- This is not a significant factor in determining melting points. The size of the molecules or ions in a substance can affect physical properties, but it's not the primary reason for the difference in melting points between these two compounds.