I had this question .....?

Question

and i dont really get whet i'm suppossed to be doing.

Explain the relative values (melting points) in terms of bonding:

Na 371K
Mg 922K
Al 933K

How do i answer this? is the higher the K value meaning there are more bonds or something?

Answer 1

yes. you are correct. the more the energy required to break the bond, the more is the melting point. so sodium has a weaker bond compared to magnesium which in turn is weaker than the bond of aluminium.

Answer 2

These are the melting points of the given elements. As the at. no. increases from Na to Al, the stength of the metallic bond increases as more electrons are cotributed to the 'sea' or 'gas' holding together the metal lattice. The rise is sharp from Na to Mg as the full shell exerts a considerable shielding on the nucleus.

Answer 3

K stands for Kelvin, which is one of the units for temperature (it is the BASE unit for temperature).
If you pull out a copy of the periodic table, you will notice that sodium (Na), magnesium (Mg) and aluminium (Al) are in the same period, but different groups. "is the higher the K value meaning there are more bonds or something?" is a misconception, as this is not really about the number of bonds, but strength of bonds. since we are going from left to right across a period in the periodic table, then there is one more proton in Mg than in Na, Al than in Mg, so the forces of attraction or bonds (if you prefer) in each compound is stronger across the period. this can also be explained by the effective nuclear force reason, as thare is no increase in shells, then the radii of the atoms stay the same, but since theres an extra proton everytime we move one across the period, then the nuclear force (force attracting electrons to the nucleus) is increasingly greater and stronger...if we take the number of full inner shells in an atom away from the number of protons in the nucleus of the same atom, then we get the effective nuclear force. if you calculate the effective nuclear force of Na, Mg and Al, you will notice that it increases from Mg to Al, hence you can say that bonds will be stronger as effective nuclear force that attracts electrons is greater in Al than in Mg and Na, so more energy will be required to break the bonds between the atoms and hence melt the compound.

Answer 4

K represents Kelvin which is a measure of temperature. the higher the melting point temperatures, the more energy is required to separate the atoms so as to form the liquid state.

Na, Mg and Al are in the same Period (same number of electron shells) of the Periodic Table, but are in Groups 1, 2 and 3 respectively. As they are metals, their ions are held together with the presence of free electrons in a metallic bonding.

Na --> Na+ + e-
Mg --> Mg2+ + 2e-
Al --> Al3+ + 3e-

As Al has more free electrons present, it is harder to separate the Al ions to form the liquid state as opposed to Na.

Answer 5

The 'K' simply refers to the melting point temperature in 'Kelvin'
(Absolute) figures.

Answer 6

K is likely to stand for Kelvin, it is another temperature scale with zero kelvin, being absolute zero. check your text book for info on Kelvin