(a) What happens when a Ferromagnetic or Ferrimagnetic solid is heated ? (b) The ions of MgO and NaF all have the same number of electrons and intermolecular distance are about the same (235 & 215 pm). Why are the melting points are so different (2642 °C & 992 °C ?

(a) What happens when a Ferromagnetic or Ferrimagnetic solid is heated ? 

(b) The ions of MgO and NaF all have the same number of electrons and intermolecular distance are about the same (235 & 215 pm). Why are the melting points are so different (2642 °C & 992 °C ?
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1 Answer

Answer :

(a) It changes into paramagnetic at hight temperature due to randomization of spins. 

(b) The ions in MgO carry two unit charges. In NaCl only one unit charge. Hence electrostatic forces of attraction in MgO are stronger.
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