Planning open questions: explaining the structure of a gold atom

Sometimes, examiners just chuck a big question at you to see how you cope. It’s quite normal for GCSE chemistry to cover parts of how atoms work, like ionic bonding, covalent bonding, the nucleus and how it attracts electrons. But take this question, from an AQA A 4406 paper:

Gold atom question
Four marks: about half of a grade on this 90-mark paper. Where to start? Well…

Bohr_atom_animation_2Put a list together of key words

If you really don’t know where to start with this, it might be best just to doodle. Draw an atom. Think about what’s in it. That gives us:

  • A nucleus, made of protons and neutrons.
  • Electrons around the nucleus, arranged in shells.

That gets us the first mark. Why only one? Because that’s just describing an atom. Any atom.  So…

File gold swords under 'awesome but impractical'.
File gold swords under ‘awesome but impractical’.

Gold, gold, gold

We’ve been asked to describe a gold atom specifically, not just any atom. That wording is really important. We need to link those points up to the specific facts about gold you can get from the periodic table:

Atomic number: 79
Mass number: 197

Let’s convert those into actual facts:

Protons: 79
Electrons: 79
Neutrons: mass number – atomic number = 197 – 79 = 118

We can write that all up now.

Final answer

Gold atom answerThe mark scheme says maximum one mark for describing the structure of an atom: 3 of the four marks are for specifically listing facts about gold.

(Source: AQA Science A SCA1HP paper, June 2012)

Acknowledgements:

Gif of an atom: ‘Kurzon’, released under this license.
Official portrait of His Majesty: Pascal, released under this license. All pictures used with thanks.

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