Locate the row containing lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). Look up these elements in the periodic table e, and click each element to reveal its
properties. Explain why Mendeleev might have grouped these elements together.

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: