The world is composed of a seemingly endless array of materials
that vary widely in shape, color, feel, density, texture, and
flexibility, yet they are all composed of about 100 chemical
elements bound together in various configurations. It is widely
believed that all of the elements on Earth were forged in the
fiery explosion of the Big Bang. Only a few elements are
abundant in the universe. The most abundant element is hydrogen,
which makes up about 75 percent of the universe. The second most
abundant element is helium, which makes up almost all the
remaining 25 percent. Oxygen is the third most abundant element.
All of the other elements are rare. The elements that are most
abundant on Earth vary from those that are most abundant in the
universe. Forty-six percent of the Earth's mass is from oxygen.
Silicon is the second most abundant element, constituting about
28 percent of the Earth's crust, followed by aluminum, iron,
calcium, sodium, potassium, and magnesium. These elements
together comprise about 98.