CIE iGCSE Co-Ordinated Science C2.2 Atomic structure and the Periodic Table Exam Style Questions Paper 1
▶️ Answer/Explanation
In the nuclide notation \( ^{A}_{Z}\text{X} \):
- The top number (A) is the nucleon number (mass number), which is the total number of protons and neutrons in the nucleus.
- The bottom number (Z) is the proton number (atomic number), which is the number of protons in the nucleus.
For \( ^{15}_{9}\text{F} \):
- Nucleon number = 15
- Proton number = 9
The number of neutrons is found by subtracting the proton number from the nucleon number:
\(\text{Number of neutrons} = 15 – 9 = 6\)
Therefore, this atom of fluorine has 6 neutrons. Option A is correct.
✅ Answer: (A)
▶️ Answer/Explanation
The ion \(^{25}_{12}\text{Mg}^{2+}\) has a proton number of 12, which means it contains 12 protons. The nucleon number is 25, so the number of neutrons is \(25 – 12 = 13\). Since it has a \(2+\) charge, it has lost 2 electrons, meaning it has \(12 – 2 = 10\) electrons. Therefore, the correct row is D: 13 neutrons and 10 electrons.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
Number of neutrons = nucleon number − proton number. So, \(31 – 15 = 16\).
The atom contains 16 neutrons.
Protons and electrons would each be 15 in a neutral atom.
✅ Answer: (B)
The atom contains 16 neutrons.
Protons and electrons would each be 15 in a neutral atom.
✅ Answer: (B)
▶️ Answer/Explanation
Protons have a relative mass of 1 and a positive charge (+1). Neutrons also have a relative mass of 1 but carry no charge. Electrons have a negligible relative mass (approximately 1/1840) and a negative charge (-1). Therefore, option B is the only correct statement.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
In the nuclide notation \(^{A}_{Z}\mathrm{X}\), the top number \(A\) is the nucleon (mass) number. For \(^{40}_{19}\mathrm{K}\), the nucleon number is 40. The proton number is 19, and the number of neutrons is 21 (40 – 19).
✅ Answer: (C)
✅ Answer: (C)