atoms of the element, and we might call this the macroscopic form of the element. There is yet a further complication. As we will see in more detail in Section 4.9, the macroscopic forms of several elements contain molecules rather than individual atoms as the fundamental components. For example, chemists know that oxygen gas consists of molecules with two oxygen atoms connected together (represented as OOO or more commonly as O2). Thus when we refer to the element oxygen we might mean a single atom of oxygen, a single O2 molecule, or a macroscopic sample containing many O2molecules. Finally, we often use the term element in a generic fashion. When we say the human body contains the element sodium or lithium, we do not mean that free elemental sodium or lithium is present. Rather, we mean that atoms of these elements are present in some form. In this text we will try to make clear what we mean when we use the term element in a particular case