9781422279465

Helium: INTRODUCTION

A Useful Gas

L ook around you. What do you see? A book and, per- haps, a half-eaten blueberry muffin, sit on your desk. Outside your window, you might see clouds or rain or the sun shining, while you can feel your heart pump your blood throughout your body. All of those things—the sol- ids, liquids, and gases around you—are composed of elements of the periodic table. The periodic table is an arrangement of all the naturally occurring, and manufactured, elements known to humans. An element is a substance that cannot be broken down into other,

WORDS TO UNDERSTAND isotope an atom of a specific element that has a different number of neutrons; it has the same atomic number but a different atomic mass

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