Elements

Definition

Elements are pure substances consisting of only one type of atom, defined by their unique number of protons. They are the building blocks for all matter in the universe.

5 Must Know Facts For Your Next Test

1. Each element is defined by its atomic number, which is the number of protons in its nucleus.
2. Elements are organized in the periodic table based on their atomic number and properties.
3. An element cannot be broken down into simpler substances by chemical means.
4. The most abundant elements in living organisms include carbon, hydrogen, oxygen, and nitrogen.
5. Isotopes are variants of elements with different numbers of neutrons but the same number of protons.

Review Questions

• What defines an element's identity?
• How are elements arranged in the periodic table?
• Which four elements are most abundant in living organisms?

Related terms

Atom: The smallest unit of an element that retains its chemical properties.

Isotope: Atoms of the same element with different numbers of neutrons.

Molecule: A group of two or more atoms bonded together.