Answer:
Neon (Ne)
Hydrogen (H)
Argon (Ar)
Iron (Fe)
Calcium (Ca)
Deuterium, an isotope of hydrogen that has one proton and one neutron.
Plutonium (Pu)
F-, a fluorine anion.
Explanation:
I got u
The compound sodium carbonate is a strong electrolyte because it completely dissociates when placed in water into its component ions. The equation of the reaction can be expressed as:

The dissociation leads to the formation of sodium and carbonate ions with the latter held together by its internal covalent bond.
This is unlike weak electrolytes that do not dissociate completely in water or aqueous solutions. Only a small fraction of the solute exists as ions in the solution.
More on strong and weak electrolytes can be found here: brainly.com/question/3410548
You need to calculate the atomic weight of that element.
number of moles = mass / atomic weight
atomic weight = mass / number of moles
atomic weight = 209.1 / 3 = 69.7 g/mol
The element produced will be gallium, Ga.
Total change in energy = Heat produced by system + work done on the system
= 228 - 55
= 173 kJ
Because this energy is released as heat, the reaction is exothermic.