What is a suitable measuring the distance between the atomatic particles?

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation: