Why Does Melting Temperature Increase from Sodium to Aluminium?

[jsmith613]

Explain why the melting temperature increases from sodium to aluminium.

Why does it have to do with ions and not atoms?

 

[Borek]

If the question is about melting metals - ions have nothing to do with it.

 

[jsmith613]

If the question is about melting metals - ions have nothing to do with it.

The markscheme clearly stated that ions must be mentioned (the question is copied word for word)

 

[jsmith613]

The markscheme clearly stated that ions must be mentioned (the question is copied word for word)

As it stated this as the answer, is it now possible to answer the original question

 

[DeeNos]

The melting temperature of a substance is influenced by various factors, including the strength of intermolecular forces, the size and shape of the atoms or ions, and the overall structure of the material. In the case of the periodic trend from sodium to aluminium, the increase in melting temperature can be attributed to the change in the size and structure of the atoms or ions.

Sodium, with its atomic radius of 186 picometers, has a relatively small size compared to aluminium, which has an atomic radius of 143 picometers. As we move from left to right across the periodic table, the atomic radius decreases due to the increasing number of protons in the nucleus, resulting in a stronger attraction between the positively charged nucleus and the negatively charged electrons. This leads to a higher melting temperature as more energy is required to overcome these attractive forces and cause the substance to change from a solid to a liquid state.

Moreover, when comparing the melting temperatures of sodium and aluminium, we must also consider the difference in their ionic structures. Sodium exists as a simple monatomic ion (Na+), while aluminium forms a more complex ionic compound with a 3+ charge (Al3+). This means that in aluminium, there are more ions per unit volume, resulting in a higher density and a stronger ionic bonding. This stronger bonding requires more energy to break, leading to a higher melting temperature.

In summary, the increasing melting temperature from sodium to aluminium can be explained by the decrease in atomic size and increase in ionic bonding strength as we move across the periodic table. This highlights the significance of both atomic and ionic structures in determining the physical properties of a substance.