Questions where students often pick the tempting wrong answer — make sure you know the right one:
Why does atomic radius increase down a group?✗ Atoms get bigger down a group because they have more protons attracting more matter.✓ Each successive element has an additional electron shell, increasing the distance of outer electrons from the nucleus.
Why does first ionisation energy generally increase across a period?✗ Atoms get bigger across a period, making electrons easier to add but harder to remove.✓ Nuclear charge increases while shielding stays roughly constant, so electrons are held more tightly.
Why is the 4s orbital filled before the 3d orbital?✗ Because the 4s shell is closer to the nucleus than the 3d shell.✓ Because the 4s orbital has a lower energy than 3d when both are empty, so electrons fill it first.
Why does Al have lower 1st IE than Mg?✗ Al has more shielding from core✓ 3p electron easier to remove than 3s
Why do metals conduct electricity?✗ Metal atoms themselves move to carry the current.✓ Delocalised electrons are free to move through the lattice of positive ions, carrying charge.
Practise Periodicity & Inorganic — free games
Test yourself with these quick revision games for this topic:
Teaching A-Level Chemistry? Free interactive lessons to set as class work, homework or cover. No student login. AQA · Edexcel · OCR · Eduqas/WJEC · CCEA
