The correct statement about magnesium [Mg] and calcium [Ca] is:
They both have the same number of valence electrons.
Both magnesium and calcium are in Group 2 of the periodic table, which means they each have 2 valence electrons.
The other statements are incorrect because:
- Neither magnesium nor calcium is classified as a noble gas; noble gases are found in Group 18.
- Magnesium (atomic number 12) has 3 electron shells, while calcium (atomic number 20) has 4 electron shells.