Complete the Henderson hasselbalch equation with the correct species

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

the electrical  conductivity  of asolution  of an electrolyte is measured by determining the resistance of thesolution  between two flat or cylindrical electrodes separated by a fixed distance.

with this one i know the answer in craters one reason i looked it up and i learned about it there is my evidence

it takes on an electronical energy