What Makes It a Different Element?So, you may be asking yourself what makes one material a different element from another? How can you tell if two chemicals are the same element? Sometimes examples of a pure element look very different from each other. For example, diamond and graphite (pencil lead) are both examples of the element carbon. You wouldn't know it based on appearance or properties. However, atoms of diamond and graphite each share the same number of protons. The number of protons, particles in an atom's nucleus, determines the element. Elements on the periodic table are arranged in order of increasing numbers of protons.
Examples of ElementsThe element with one proton is hydrogen. Helium contains two protons and is the second element. Lithium has three protons and is the third element, and so on.
Pure elements contain atoms that all have the same number of protons. If the number of protons is mixed, you have a mixture or a compound. Examples of pure substances that are not elements include water (H2O), carbon dioxide (CO2) and salt (NaCl). See how the chemical composition of these materials includes more than one type of atom? If the atoms had been the same type, the substance would have been an element even though it contained multiple atoms. Oxygen gas, (O2), is an example of an element.