Just the answer. thank you

The major difference is that a histogram is only used to plot the frequency of score occurrences in a continuous data set that has been divided into classes, called bins.  bar charts, on the other hand, can be used for a great deal of other types ofvariables  including  ordinal  andnominal  data sets.

Element 17 is chlorine it is a group 7 element(halogen) and belongs to period 3 of the periodic table