Which nonmetal appears to be an exception to this guideline?

hydrogen

Explanation:

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:

explanation:

0.07 g/cm³

1.37 g/cm³