Metal to Non-MetalMost striking trends across Periodic Table are: metals to non-metals solid to gas Na, Mg and Al are clearly metals, but Si is much harder to classify. Si has the shiny appearance of a metal, but is brittle. It conducts electricity, but very poorly. Silicon is an in-between element, usually classified as a semi-metal or metalloid. Trends in Melting and Boiling PointsAlthough we can identify broad trends just from the appearance of the elements, we can learn more about the bonding and structure of the elements from their melting and boiling points.Group 1 -> 4 general increase in boiling pointsGroup 4 to 5 - sharp decrease in boiling pointsGroup 5 to 8 - comparitely low boiling pointsThere is a distinct change between Group 4 to 5 in both the physical structure of the elements and the forces holding the structures together. The change is: from giant structures to simple molecular structures from strong forces to weak forces The trend in melting point is similar to the trend in boiling point. There is a sharp decrease between Group 4 to 5 marking the change from giant to simple molecular structures. The melting and boiling points of the metals Na, Mg and Al in Period 3 increase across the period.