Drawing Dot-Cross Diagrams
Part of Ionic Bonding · GCSE GCSE Chemistry revision
This worked example covers Drawing Dot-Cross Diagrams within Ionic Bonding for GCSE Chemistry. Revise Ionic Bonding in Bonding & Structure for GCSE Chemistry with 35 exam-style questions and 20 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 6 of 16 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Topic position
Section 6 of 16
Practice
35 questions
Recall
20 flashcards
🧮 Drawing Dot-Cross Diagrams
Examiners LOVE dot-cross diagrams. Here's exactly how to draw them:
Important: do not draw the inner shells at all — only the outermost ring appears in the diagram. 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) — two electrons short of a stable configuration
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 is 1 electron short of a stable configuration
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.
Keep building this topic
Read this section alongside the surrounding pages in Ionic Bonding. That gives you the full topic sequence instead of a single isolated revision point.
Practice Questions for Ionic Bonding
Which combination of elements forms an ionic compound?
Describe the structure of an ionic compound and explain why ionic compounds have high melting points. [3 marks]
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