Physical change .. you cannot undo chemical ... physical is like bending , shattering a mirror , denting something ..
chemical would be rust or something .
Answer: A) Sodium Na and Magnesium Mg
Explanation:
In the period table, you can see that Sodium (group 1) has 11 protons, and Magnesium (group 2) has 12 protons. 11+12=23 protons