To find the mass of glucose, you must multiply the atomic weight of each of the elements in the molecule by the subscripts in the formula:



Then you add all of them together:

Therefore, the molar weight of glucose is 180.15 grams.
The molecule is non-polar, because the difference in electronegativity between the two sides of the structure equals 0. The electronegativity difference between O (3.5) and C(2.5) is 1 and also on the other side, cancelling each other.
Ionic cause Mg will give O its electrons so both their outer shells are full and stable
Becoming an ion involves gaining or losing electrons
Electrons have a relative mass of 0
So adding or removing them doesn't change the mass of the atom
So the answer is (3) remains the same