 H2O is a case in point: the relevant (chemical) relation is bonding, which links the three atoms in question. Another, often considered, example is methane as a structural property of methane-molecules (CH4), which involves a bonding relation between atoms and the joint instantiation of hydrogen (by four atoms) and carbon (by one atom). Non-relational structural properties do not require condition (iv). For instance, mass 1 kg involves many relevant properties of the kind mass n kg, for \(n \lt 1\), which are instantiated by relevant proper parts of any object that is 1 kg in mass, and these proper parts are not linked by any relevant relation (Armstrong 1978b: 70).