GCSE Atomic Structure & Periodic Table 3 — Questions and Answers
Question 1: Carbon-12 and Carbon-14 are isotopes. Which statement correctly compares them?
- They have different numbers of protons
- Carbon-14 has 2 more neutrons than Carbon-12 (Correct answer)
- Carbon-14 has 2 more protons than Carbon-12
- They have different electron configurations
Correct answer: Carbon-14 has 2 more neutrons than Carbon-12
Both have 6 protons; Carbon-12 has 6 neutrons and Carbon-14 has 8 neutrons, a difference of 2.
Question 2: Which of the following is a property of Group 7 elements (halogens)?
- They have 7 electrons in their outer shell (Correct answer)
- They are metals
- They are unreactive
- They form positive ions easily
Correct answer: They have 7 electrons in their outer shell
Halogens have 7 outer-shell electrons and need one more to complete their shell, making them reactive non-metals.
Question 3: An ion has 10 electrons and a charge of 2+. How many protons does it have?
- 8
- 10
- 12 (Correct answer)
- 14
Correct answer: 12
A 2+ charge means the atom lost 2 electrons, so protons = electrons + 2 = 10 + 2 = 12 (magnesium).
Question 4: As you move down Group 1 (alkali metals), reactivity with water:
- Decreases
- Stays the same
- Increases (Correct answer)
- First increases then decreases
Correct answer: Increases
Reactivity increases down Group 1 because the outer electron is further from the nucleus and more easily lost.
Question 5: Which electron shell can hold a maximum of 8 electrons?
- First shell
- Second shell
- Third shell
- Both second and third shells (Correct answer)
Correct answer: Both second and third shells
The second and third shells each hold up to 8 electrons at GCSE level.
Question 6: Elements in the same group of the periodic table have similar chemical properties because they:
- Have the same mass number
- Have the same number of electron shells
- Have the same number of outer shell electrons (Correct answer)
- Are in the same period
Correct answer: Have the same number of outer shell electrons
Elements in the same group have the same number of valence electrons, which dictates their chemical behaviour.
Question 7: Chlorine exists as Cl-35 (75%) and Cl-37 (25%). What is the relative atomic mass of chlorine?
- 35.0
- 35.5 (Correct answer)
- 36.0
- 37.0
Correct answer: 35.5
RAM = (35×75 + 37×25) / 100 = (2625 + 925) / 100 = 35.5.
GCSE Atomic Structure & Periodic Table 3
Carbon-12 and Carbon-14 are isotopes.
Which statement correctly compares them?