Answer: 0.5 mole Mg
Explanation: solution:
12 g Mg x 1 mole Mg / 24 g Mg
= 0.5 mole Mg
it would need to gain 2 more for it to achieve a stable configuration
the best way to remember this is the noble gasses all have 8 valence electrons and that they are the most stable elements on the periodic table
C. Distance from Earth
The observed brightness of a star (the apparent magnitude) to an absolute magnitude, you need to know the distance [d], to the star. Alternatively, if we know the distance and the apparent magnitude [m] of a star, we can calculate its absolute magnitude [d].
*paraphrased from "COSMOS.com"
Out of the options, the best indicator is a color change since it is the only one that can't really be blamed on a physical change. you will eventually notice that during qualitative labs and some quantitative labs, usually the thing that you are looking for is either color change or the production of a precipitate to indicate the presence of a chemical reaction
