Blimps, Balloons, and Models of the Atom

A The Hindenburg was filled with hydrogen, a reactive and flammable gas. Question What makes hydrogen reactive  

Why is helium inert What is it about helium atoms that makes helium gas inert By contrast, why is hydrogen so reactive Recall from Chapter 5 that elemental hydrogen exists as a diatomic element. Hydrogen atoms are so reactive that they react with each other to form hydrogen molecules. What is it about 

The periodic law stated here Is a modification of Mendeleev s original formulation. Mendeleev listed elements In order of increasing mass today we list them in order of increasing atomic number. 

When we examine the properties of hydrogen and helium, we make observations about nature. Mendeleev s periodic law, first discussed in Chapter 4, summarizes the results of many similar observations on the properties of elements  

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