The equation for the chemical reaction shown below is not balanced. what number should replace the question mark to balance this equation? 2al + ? cl2 → 2alcl3 a. the number 2 b. the number 3 c. the number 4 d. the number 5

B. the number 3.
there are 2Al's on both sides and 6 Cl's on the right side so to balance it, you multiply Cl2 by 3 to get 6 Cl's.

The mass has escaped into a gas which you can not see so the law stays true.

☆ionisation energy increases across a period from na -> ar☆ionisation energy decreases down a group from li -> fr☆ionic radius decreases across a period from na -> cl☆ionic radius increases down a groupfrom f -> ii hope it clarifies your doubts