What is the specific heat of magnesium?

I'm not sure what you are asking with this question, but here are some specs.

Magnesium
State (s, l, g) s
Melting point 922 K
Boiling point 1378 K
Heat of fusion 8.954 kJ/mol
Heat of vaporization 127.40 kJ/mol
First ionization energy 737.7 kJ/mole
Second ionization energy 1450.6 kJ/mole
Third ionization energy 7732.6 kJ/mole
Heat atomization 148 kJ/mole atoms
Electronegativity 1.31
Electron affinity kJ/mole
Specific heat 1.02 J/gK
https://www.nuclear-power.com/magnesium-specific-heat-latent-heat-vaporization-fusion/

Well, BB, heat capacity is the amount of heat energy needed to raise a substance by one unit of temperature (usually one Kelvin, which is the same as a degree Celsius).
Specific, in physics, often means per unit mass, so specific heat capacity is the heat energy (usually in joules) required to raise a fixed mass of substance (usually one kilogram) by one unit of temperature.
The standard SI unit is therefore joules per kilogram per Kelvin (J/kgK).

Water notoriously takes a lot of energy to heat it up and has a large SHC of 4,180 J/kgK.
Magnesium as a metal conducts heat through itself and its SHC is therefore much less at 1,020 J/kgK.
It has been given above in Joules per gram per Kelvin.