Trend: Melting Point Melting points of the elements across period 3 Flashcards
pattern is a little harder to see from the data, but you can see that it rises and falls
The trends in melting point can be explained by looking at the
bonding and structure of the elements
The structure of sodium magnesium and aluminium
that Na, Mg and Al are metallic elements which form positive ions arranged in a giant lattice in which the ions are held together by a ‘sea’ of delocalised electrons around them.
Why and what is the order of metals in period 3 melting point
The electrons in the ‘sea’ of delocalised electrons are those from the valence shell of the atoms
Na will donate one electron into the ‘sea’ of delocalised electrons, Mg will donate two and Al three electrons
As a result of this, the metallic bonding in
Al is stronger than in Na
This is because the electrostatic forces between a 3+ ion and the larger number of negatively charged delocalised electrons is much larger compared to a 1+ ion and the smaller number of delocalised electrons in
Na Because of this, the melting points increase going from Na to Al
the highest melting point is Silicon why
Si has the melting point due to its giant molecular structure in which each Si atom is held to its neighbouring Si atoms by four strong covalent bonds
covalent bond strongest bond
P, S, Cl and Ar are non-metallic elements and exist as simple molecules
what are there formulas
P4
S8
Cl2
Ar is atom
P, S, Cl and Ar are non-metallic elements and exist as simple molecules
what are these structures like
The covalent bonds within the molecules are strong, however, between the molecules, there are only weak instantaneous dipole-induced dipole forces
It doesn’t take much energy to break these intermolecular forces
What has the highest melting point and why P, S, Cl and Ar
Therefore, the melting points decrease going from P to Ar (note that the melting point of S is higher than that of P as sulphur exists as larger S8 molecules compared to the smaller P4 molecule)
so more idid
order of melting point highest to lowest
Si-Al-Mg-Na-S-P-Cl-Ar
