In the physical properties, it is mentioned that the element has 4 valence electrons. The elements in the periodic table are arranged such that, the number of valence electrons present in the neutral atoms belonging to a particular group is equal to the group number.
Thus, the unidentified element can be best classified as a nonmetal in period 4
Ans C)
Attraction between a cation in one element and an anion in the other element
18.4 * 10^9 lbs = (18.4 * 10^9)/2000 tons
Cost = ((18.4 * 10^9)/2000 ) * 318
Cost = $ 2925600000