Fig. 4.1 shows the nuclide (isotopic) symbols of three particles. The letters R and Q are not the real chemical symbols. All three particles are neutral ato...
Question 1 Report
Fig. 4.1 shows the nuclide (isotopic) symbols of three particles. The letters R and Q are not the real chemical symbols. All three particles are neutral atoms.
Fig. 4.1
(a) State what the numbers 23 and 11 represent for the first atom. [2]
(b) Deduce the number of neutrons in the atom shown as R with nucleon number 24. [1]
(c) The two atoms labelled R are isotopes of the same element. State the feature of their nuclide symbols that shows this. [1]
(d) Deduce the number of electrons in the outer shell of atom Q and hence its group in the Periodic Table. [2]
Answer Details
What this tests: reading nuclide symbols, counting neutrons, recognising isotopes, and deducing a group.
In a nuclide symbol the top number is the nucleon (mass) number and the bottom number is the proton (atomic) number.
(a) For the first atom, 23 is the nucleon (mass) number, the total number of protons plus neutrons [1], and 11 is the proton (atomic) number, the number of protons [1].
(b) Neutrons = nucleon number minus proton number = \(24 - 11 = 13\) neutrons [1].
(c) The two R atoms have the same lower number (proton number 11) but different upper numbers (nucleon numbers 23 and 24), which is exactly what makes them isotopes of the same element [1].
(d) Q has 20 protons, so 20 electrons arranged 2,8,8,2 [1]; with 2 electrons in the outer shell it belongs to Group II [1].
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