6/23/2023 0 Comments Atomic size trendThe stronger the induced dipole-dipole forces, the higher the melting point.The shape of a molecule and the distance between the molecules affects the strength of induced dipole-dipole forces. The melting point of these substance depends on the varying strength of van der Waals forces.For this reason, the melting points of these simple molecular substances are low. As learned earlier, van der Waals forces are weak intermolecular forces which require a small amount of energy to break.Phosphorous (P4), sulfur (S8) and chlorine (Cl2) are simple molecular substances which consist of van der Waals forces.The change in melting point from Phosphorous to Chlorine (P to Cl) These strong covalent bonds require a large amount of energy to break and therefore silicon has a high melting point.ģ.As we learned earlier, macromolecular structures have strong covalent bonds that hold the atoms together.Silicon has a macromolecular structure which consists of covalent bonding.This is because there is a greater electrostatic attraction between the positive ions and delocalised electrons and hence the metallic bond is stronger and requires more energy to break.As we move across period 3 the number of delocalised electrons per metal atom increases and the radius of the elements decreases.As well learned earlier, the more delocalised electrons present and the smaller the radius of the atom, the higher the melting point of the metal.Sodium, magnesium and aluminium are all metals and therefore have metallic bonding.The change in melting point from Sodium to Aluminium (Na to Al). We will now discuss the trend in melting points across Period 3:ġ.
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