CAIE A Level Chemistry 9701 · Atomic structure

Atomic structure: explain question

Explain5 marksChallenge

Neon has three naturally occurring isotopes. Two of them are described below.

Neon-20 atoms contain 10 protons and 10 neutrons. Neon-22 atoms contain 10 protons and 12 neutrons.

(a) Define the term isotope. (b) Write the symbol for each isotope in the form $^x_y\ce{Ne}$ , where x is the mass number and y is the proton number. (c) Explain why the two isotopes have the same chemical properties. (d) Explain why the two isotopes have different physical properties. You should refer to mass and density.

How this question is marked

5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.

Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.

Atomic structure: explain question

How this question is marked

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