Yes, magnesium oxide (MgO) will eventually
dissociate when it is heated, but not until very
high temperatures. In fact, MgO, like other ionic
compounds, does not dissociate appreciably until
it melts. The melting point of MgO is 2827°C,
which is very high – almost as high as the melting
point of iron. In molten MgO, the Mg2+
and O2- ions can move freely and
conduct electricity. If MgO is heated even hotter
to its boiling point at 3600°C, it can dissociate
in the gas phase into gaseous ions.
Wriedt, H.A. “The Mg−O (Magnesium-Oxygen) system.”
Bulletin of Alloy Phase Diagrams 1987, 8, 3,
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