For the answer to the question above, The difference in melting points for ionic compounds can be explained by the size of the ions themselves; smaller ions are able to get closer, and this increases the strength of the electrostatic charge between them. Another factor affecting the melting point of ionic compounds is the number of charges on the ion. For example, magnesium oxide has a charge of +2 and -2, which is stronger than sodium chloride's ionic charge of +1 and -1.
