All of the group 2 are good conductors of electricity becuase they have metallic bonds meaing there are mobile, delocalised electrons surrounding the possitive ions.
The radii increase going down the group becuase a new shell of electrons is present with each next element.
When the group 2 elements react they lose their 2 outer electrons so become possitive 2+ ions.They are all oxidised when they react becuase their oxidation numbers increase from 0 in the element to +2 in the ion.
Reaction with oxygen:
All tarnish in air and burn when heated. When magnesium is heated in air…