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IGCSE · Practice questions · Atomic structure and the Periodic Table

Count the particles.

Six original Cambridge-style questions on atomic structure: the three particles, proton and mass number, configurations of the first 20 elements and the link to the Periodic Table.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

Two numbers tell you everything.

01
Recall
[3 marks]

Copy and complete: give the relative charge and relative mass of a proton, a neutron and an electron.

  • Proton: relative charge +1, relative mass 1. ✓
  • Neutron: relative charge 0, relative mass 1. ✓
  • Electron: relative charge −1, relative mass 1/1836. ✓
02
Recall
[2 marks]

Define proton number and mass number.

  • Proton number: the number of protons in the nucleus of an atom. ✓
  • Mass number: the total number of protons and neutrons in the nucleus of an atom. ✓
03
Calculation
[3 marks]

For an atom of 3919K, state the number of protons, neutrons and electrons, and write its electronic configuration.

  • 19 protons and 19 electrons. ✓
  • 39 − 19 = 20 neutrons. ✓
  • Configuration 2,8,8,1. ✓
04
Analysis
[3 marks]

Element X has the electronic configuration 2,8,3. State its group and period, and identify the element.

  • Three outer-shell electrons: Group III. ✓
  • Three occupied shells: Period 3. ✓
  • 2 + 8 + 3 = 13 electrons, so proton number 13: aluminium. ✓
05
Explain
[2 marks]

An atom contains charged particles. Explain why the atom has no overall charge.

  • The number of electrons equals the number of protons. ✓
  • Each proton has charge +1 and each electron −1, so the charges cancel (neutrons have no charge). ✓
06
Analysis
[3 marks]

An atom of element Y has mass number 40 and contains 22 neutrons. Identify Y, give its electronic configuration and explain whether it is likely to be reactive.

  • Protons = 40 − 22 = 18, so Y is argon. ✓
  • Configuration 2,8,8. ✓
  • Its outer shell is full, so it is a noble gas and is unreactive. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.