I still dont understand from the msg given... another explanation any1 Hey I have two questions... the first one I did I got wrong but am really unsure why... I used sigma=Q/A but didnt get the right answer... I got that the answer was 1.3277E7 but I am so far off it aint funny! Please could someone help! The answer is meant to be 117.5! I dunno tho! Consider a cell whose cell membrane is 4.7 nm thick and whose resting potential is 62.4 mV. What is the approximate surface charge density (in µ C/m2) on the outside wall of the cell? Also this question also has me stumped! Consider the helium atom which consists of two electrons orbiting a nucleus made up of two protons and two neutrons. If both electrons are at a distance of r = 4.5 × 10-11 m away from the nucleus, as in figure, what is the potential energy (in eV) of the helium atom? Treat the nucleus as pointlike. - Give answer to 4 significant figures. I thought you'd just find the energies of the electron on the helium atom which I got was 1.024E-17 and add them but obviously you dont so if anyone knows wat to do I would be much appreciative, I really just needa know how to do it... or even just a general start!