What is the charge on a magnesium ion? how do they get that charge?

A) Magnesium is in group 2. That means it has two electrons in its outer shell when these are lost, a magnesium ion is formed Mg2+ is formed. 

b) A magnesium ion get its charge because it has the two electrons in the outer electron shell of a magnesium shell. Both are lost when it changes to an ion leaving it with 12 positively charged protons and 10 negatively charged electrons. This produces a +2 positive charge.

8.7 degrees celsius and 15.6 degrees fahrenheit

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.