State whether the following statements are True or False.
(a) Organic compounds having different molecular formula, but same structural formula are called isomers.
(b) A salt is a compound formed by partial or complete replacement of the hydrogen ion of an acid by a metal or electropositive ion.
(a) False: Isomers are compounds that have the same molecular formula but different structural formulas.
(b) True: This is the chemical definition of a salt. For example, replacing H^+ in H_2SO_4 with Na^+ gives NaHSO_4 (partial replacement) or Na_2SO_4 (complete replacement).
Which of the following element pairs will form an ionic bond? 


During the ventricular systole, the atrioventricular valves (P) ________ and the semilunar valves (Q) _________.