Which statement best describes an element?

An element is defined as a pure substance that is made up of only one type of atom. This means that all the atoms in an element have the same number of protons, which is unique to each element and defines its identity on the periodic table. For example, hydrogen has one proton, while carbon has six protons; these unique numbers distinguish one element from another.

The definition emphasizes the purity of elements, indicating that they cannot be divided into simpler substances through chemical means. This is in contrast to compounds, which consist of different types of atoms bonded together, and mixtures, which combine multiple substances without chemical bonding. Additionally, an element cannot be broken down into simpler constituents, reinforcing the idea that it is the most basic form of matter.

The identification of an element as a single type of atom is fundamental in chemistry, as it lays the groundwork for understanding chemical reactions, the formation of compounds, and the properties of different materials.