The "periodic table" category contributes slightly more towards predicting the shear modulus compared to the bulk modulus as shown in Fig. ). Within this category, two important attributes are the atomic number and covalent radius of an element. Both factors play a role in determining the elastic properties of a material. Elements with higher atomic numbers generally exhibit stronger interatomic bonding, leading to higher bulk and shear moduli. On the other hand, larger covalent radii result in longer and weaker covalent bonds, leading to lower elastic moduli . For example, a diamond, which is made up of carbon atoms with small covalent radii, has short and strong bonds, leading to high elastic modulus and hardness. On the other hand, NaCl, composed of sodium and chlorine atoms, has longer and weaker bonds due to the larger covalent radius of chlorine, resulting in lower elastic modulus and hardness.