Which of these ions cannot form both high-spin and low-spin octahedral complexes

All the elements are arranged by melting points on the periodic table. in row they go from metals to gasses. in the row from sodium to argon, sodium is more reactive than the one on its right, magnesium.

Ansaquatic plants;  

Moles = mass/molar mass by this formula 458/207+32 you should get your answer the ans. is 1.916 mol to 4 sig. fig.

Hope you figure it out: )