Answer:
1.5min
Explanation:
To solve the problem it is necessary to take into account the concepts related to Period and Centripetal Acceleration.
By definition centripetal acceleration is given by

Where,
V = Tangencial velocity
r = radius
With our values we know that


Therefore solving to find V, we have:



For definition we know that the Time to complete are revolution is given by




Answer:
Helium
Explanation:
Helium is the least reactive element, since it is a noble gas with the smallest amount of valence rings.
The correct answer would be the last one
I know that protons and neutrons are located at the center of an atom, so the correct answer is D