1
$\begingroup$

There was a question asking why magnesium metal has a higher melting point than sodium.

In the answer, they said:

  • Magnesium has more delocalised electrons.
  • Magnesium ions have a greater positive charge.
  • Magnesium has a greater electrostatic attraction between ions and delocalised electrons.

However, in the mark scheme in the additional guidance, it also said the mark couldn't be given if you said:

Magnesium ions have a great nuclear charge rather than greater positive charge.

I was confused as to what the difference is.

|improve this question
$\endgroup$
  • 1
    $\begingroup$ What is your weight? Now what is the weight of your skeleton? Is there any difference? $\endgroup$ – Ivan Neretin May 5 '18 at 7:34
  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Loong♦ May 6 '18 at 6:45
1
$\begingroup$

Nuclear charge is the charge present inside a nucleus, due to the protons. For example, a carbon atom has $+6e$ nuclear charge.

Ionic charge is the charge due to the gain or loss of electrons in the valence shell. So, the sodium ion has an ionic charge of $+1e$ (due to loss of one valence electron). That ion's nuclear charge is still $+11e$ (there are still 11 protons only).

The reason because nuclear charge as an answer to this question is unaccetable is because nuclear charge - being inside the nucleus - has largely no affect on the intermolecular forces between the magnesium atoms. Those magnesium atoms have intermolecular forces governed only by the valence electrons only.

|improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.