This worked example covers Drawing Dot-Cross Diagrams within Ionic Bonding for GCSE Chemistry. Revise Ionic Bonding in Bonding & Structure for GCSE Chemistry with 27 exam-style questions and 20 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 5 of 13 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Topic position
Section 5 of 13
Practice
27 questions
Recall
20 flashcards
🧮 Drawing Dot-Cross Diagrams
Examiners LOVE dot-cross diagrams. Here's exactly how to draw them:
1. Draw Na with its electrons as DOTS (only show outer shell: 1 dot)
2. Draw Cl with its electrons as CROSSES (7 crosses in outer shell)
3. Show the electron transferring (the dot moves to Cl)
4. Draw square brackets around each ion
5. Write the charge OUTSIDE the brackets: [Na]⁺ and [Cl]⁻
The transferred electron is still shown as a dot on chlorine!
1. Mg has 2 outer electrons (2 dots)
2. O has 6 outer electrons (6 crosses) — needs 2 more
3. BOTH electrons from Mg transfer to O
4. Mg becomes Mg²⁺ (lost 2 electrons)
5. O becomes O²⁻ (gained 2 electrons)
Square brackets and charges are essential for full marks!
1. Mg has 2 outer electrons to lose
2. Each Cl only needs 1 electron
3. Solution: Mg gives 1 electron to EACH of 2 Cl atoms
4. Mg becomes Mg²⁺, both Cl become Cl⁻
5. Formula is MgCl₂ because you need 2 Cl⁻ to balance Mg²⁺
Quick Check: Sodium (Na) has electron configuration 2,8,1. What ion does it form, and why?
Na⁺ — sodium loses its 1 outer electron to achieve a stable full outer shell (2,8, like neon). Losing an electron means it has more protons than electrons, giving a +1 charge.