What property do the following elements have in common? sulfur, iodine, and magnesium a) same phase at room temperature. b) good conductors of electricity. c) same number of valence electrons. eliminate d) they form cations (positive ions).

Sulphur (S), Iodine (I) and Magnesium (Mg) are all three, solids at the room temperature. Thus they have the same phase at room temperature. 
Sulphur and Iodine are not good conductors of electricity.
Also while Sulphur is in group 6, Magnesium is in group 2. Therefore they do not have the same number of valence electrons. Sulphur is making anions (negative ions) and Magnesium is making cations (positive ions).

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