Answer:
The heat of reaction is basically the energy that is being released and or absorbed when chemicals are transformed in a type of chemical reaction. However, the heat of reaction or also called reaction enthalpy is mostly or typically expressed as a molar enthalpy in kJ/mol and or as just a specific enthalpy in kJ/kg or kJ/L.
Metals are insulators and malleable. Hope this helps even though I'm late :)
Reactivity trends of halogen:
1) Melting point and boiling points increased down the
group
2) Colour becomes darker.
E.g. Fluorine (pale yellow)
Chlorine (yellowish-green)
Bromine (reddish-brown)
Iodine (purplish-black)
Astatine (black)
3) The reactivity decreases down the group.
Reactivity:
F > Cl > Br > I > At
