Why does na have a low melting point

Use this information to describe how melting point changes in group 1. Going down group 1, the melting point decreases. Use the information in the table to predict the melting point of francium, Fr. Explain your answer. This is because francium is below caesium in the periodic table, so it should have a lower melting point, and the difference in melting point decreases going from one element to the next.

Physical properties of the group 1 elements Group 1 contains elements placed in a vertical column on the far left of the periodic table. Group 1 is on the left-hand side of the periodic table The alkali metals share similar physical and chemical properties. Therefore metallic bond becomes stronger and melting point increases from sodium to aluminium. In fact the metallic bond in sodium and other Group 1 metals is so weak that the melting point of sodium is unusually low and falls within the region of simple molecules.

Silicon is a macromolecule or giant molecule with strong and extensive covalent bonds. Therefore a lot of energy is required to overcome these covalent bonds and melting point for silicon is very high. The melting point of Si is the highest in Period 3 elements but do take note this doesn't mean all giant molecules have higher melting points than all metals. Each silicon atom is covalently bonded to four other silicon atoms in a tetrahedral arrangement.

These elements are non-metals. Phosphorus, sulfur and chlorine exist as simple molecules with van der Waals' forces between them. Argon is monatomic — it exists as separate atoms.

There are are van der Waals' forces between its atoms. The melting and boiling points of these elements are very low because:. Phosphorus exists as P 4 molecules, sulfur exists as S 8 molecules, chlorine exists as Cl 2 molecules and argon exists individual atoms.

The strength of the van der Waals' forces decreases as the size of the molecule decreases, so the melting points and boiling points decrease in the order:. The atoms in molecules of phosphorus, sulfur or chlorine are attracted to each other by covalent bonds. These bonds are much stronger than the van der Waals' forces between the molecules: the covalent bonds do not break during the state changes of these elements.

All Rights Reserved. Melting and boiling points across period 3. Learning outcomes After studying this page, you should be able to: describe and explain the trends in melting and boiling points across period 3.