Explain how chemists can state with certainty that no one will discover an element that would appear on the periodic table between sulfur and chlorine

the answer is f1 and d2 because if you put equal force on those two points the beam would balance trust me on this

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =