Answer:
It is mentioned that the student is mixing chemicals A and B and observes the time taken for the color to change. However, in the experiment, it is noticed that the student has repeated the procedure five times and each time he or she is modifying the concentration of chemical B. Thus, it is clear that the concentration of chemical B is the independent variable in the experiment. An independent variable is illustrated as the variable, which is controlled or modified in the experiment.
Actually, I strongly believe it is a switch.
Bohr model is valid only for hydrogen and hydrogen-like species, but quantum mechanical model can explain all elements....
22) Oxygen with a -2 charge
23) Neon with a +2 charge
24) Fluorine with a -1 charge
25) Lithium with a +1 charge
