An athlete is running a 5-km race at an average speed of 8 km/h. she has to stop to tie her shoe. after tying her shoe, she continues running at 8 km/h. why would her average speed for the entire race be less than 8 km/h? .

each chemical family is represented as a group or column on the periodic table. based on chemical properties, there are 6 types of chemical families. group 1 represents alkali metals, group 2 represents alkaline earth metals, groups 3 to 12 represent transition metals, groups 13 to 16 represent non-metals and other metals, group 17 represents halogens and group 18 represents noble gases.