Scientists Say: Element

Element (noun, “EL-eh-mint”)

An element is a pure substance made of only one type of atom.

Each atom consists of three smaller particles. These are electrons, neutrons and protons. The number of protons determines what element an atom is. (For example, all carbon atoms have six protons.) That’s why chemists give the number of protons a special name: atomic number. (Carbon’s atomic number is six.) Atoms of the same element can contain different numbers of neutrons. Their electron number can vary too.

Ninety-two elements occur naturally on Earth. The lightest is hydrogen. Each of its atoms has only one proton. One of the heaviest elements on Earth is uranium. Each atom of uranium contains 92 protons. An atom of uranium weighs about as much as 238 hydrogen atoms.

Scientists can create new elements in the lab. Curium — with 97 protons — is one example. This element doesn’t occur naturally on Earth.

A chart called the periodic table organizes all known elements. They are arranged according to their atomic number and other properties. The table also groups similar elements into chemical families. One example is the noble gases. This family includes helium, neon and krypton. With very few exceptions, these elements do not carry out chemical reactions. That sets them apart from other chemical families.

In a sentence

Scientists study ancient black holes to learn more about how our lightest elements — hydrogen and helium — might have formed.

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