Write the chemical formula for
a) barium chloride (ba ion, 2 cl ion)
b) sodium sulfide (2 na ion, 1 s ion)

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: