Sodium chloride is written as NaCl and is composed of one sodium ion and one chloride ion. Calcium chloride is written as CaCl2 and is composed of one calcium ion and two chloride ions. How do you know that two chloride ions are required to make calcium chloride (you may use a LDD for the ionic bond between calcium and chlorine or write it out in words)?

The ionic compound should be neutral overall. For metals and nonmetals to react they have to lose their charges to reach to that neutrality. So we are trying to ensure the compound is neutral after they react. ( the reactants I mean)

Like Na+ whose has 1 electron to lose and Cl- who has one electron to gain to achieve stability are very compatible. So they cancel each other. +1 -1 = 0

Its the same concept for CaCl2. Ca has a 2+ charge and 1 Cl by it self, has a -1 charge. in order for neutrality to cancel each other timing Cl by 2 allows it to achieve the criteria to cancel the 2+ charge on Ca.

2 × -1= -2

So Ca 2+ +Cl 2- = 0

I hoped I explained it right

answer; /// i do believe that the correct answer is (a) boiling