Home / AS & A Level Chemistry 1.1 Particles in the atom and atomic Radius Exam Style Practice Questions Paper 1
In which row do the particles increase in size?
| Smallest | → | Largest | |
|---|---|---|---|
| A | N | O | F |
| B | \( \mathrm{N^{3-}} \) | \( \mathrm{O^{2-}} \) | \( \mathrm{F^-} \) |
| C | \( \mathrm{Na^+} \) | \( \mathrm{Mg^{2+}} \) | \( \mathrm{Al^{3+}} \) |
| D | \( \mathrm{Na^+} \) | Ne | \( \mathrm{F^-} \) |
Correct Answer: \( \boxed{\mathrm{D}} \)
The particles in option D are isoelectronic; they all have 10 electrons.
For isoelectronic species, ionic or atomic radius increases as nuclear charge decreases.
Nuclear charge:
Hence the sizes increase in the order:
\( \mathrm{Na^+ < Ne < F^-} \)
Therefore, the correct answer is (D).
How many neutrons are contained in an atom of iron with a mass number of 60?
Correct Answer: \( \boxed{\mathrm{C}} \)
The number of neutrons is calculated using:
\( \mathrm{Number\ of\ neutrons = Mass\ number – Atomic\ number} \)
Iron has an atomic number of \( \mathrm{26} \).
Therefore:
\( \mathrm{Number\ of\ neutrons = 60 – 26 = 34} \)
Hence, the correct answer is (C).
Compound X contains two elements, Y and Z. Element Y is in Period 2 of the Periodic Table. In one atom of element Y, the p sub-shell has all three orbitals occupied; only one of these three orbitals is fully occupied. Element Z is in Period 3 of the Periodic Table. In one atom of element Z, the p sub-shell has only two orbitals occupied. What is the formula of compound X?
Ans: C
Element Y is in Period 2 with three p-orbitals occupied, but only one fully occupied (2 electrons). This gives Y an electron configuration of \(1s^2 2s^2 2p^2\), which is Carbon (C). Element Z is in Period 3 with two p-orbitals occupied, giving an electron configuration of \(1s^2 2s^2 2p^6 3s^2 3p^2\), which is Silicon (Si). The stable compound formed between Carbon and Silicon is SiO₂ (Silicon dioxide), as Carbon does not form a stable binary compound with Silicon, and the other options do not fit the given conditions.