10.4Chapter 10: Structure, Bonding, and Properties

Inside ionic compounds — Alhussan Chemistry - Stage 9 Revision Notes & Topical Questions

5 min read 8 parts Lesson 4 of 9 2 quizzes

📚 Alhussan Chemistry - Stage 9 Hub / Topical Revision

0%read

Lesson summary

10.4 Inside ionic compounds — Giant Ionic Lattices and Electrostatic Bonds — Alhussan International Academy — Chemistry (Stages 7–9) notes: Define ionic bonding, ionic compound and giant ionic structure, and explain the properties of ionic compounds using the giant ionic model.Io…

Bonds act in all directions
Brittleness
Stronger attraction
Insoluble compounds
Sodium chloride
Magnesium chloride

Part 1 of 6Ionic bonding

Ionic bonding

Ionic bonding the electrostatic attraction between positive and negative ions.

A crystal of sodium chloride (NaCl) is made of millions of sodium ions and chloride ions held together this way.

Formation

Formation an ionic bond forms when a metal atom transfers outer electrons to a non-metal atom.
Sodium (2,8,1) gives one electron to chlorine (2,8,7), forming Na⁺ and Cl^-, each with a full outer shell.

Ionic compound

Ionic compound a compound made up of positive and negative ions, and most compounds of a metal and a non-metal are ionic.

Calcium oxide and nickel chloride are also ionic compounds.

Part 2 of 6Giant ionic structure

Giant ionic structure

Giant ionic structure the three-dimensional pattern of oppositely charged ions held in the solid state.

Lattice

Lattice ions pack in a regular repeating pattern called a giant ionic lattice, with each ion surrounded by ions of the opposite charge.

Bonds act in all directions

Bonds act in all directions the attraction acts throughout the crystal, and ionic compounds do not form single molecules.

Formula

Formula it shows the simplest ratio of ions, for example NaCl is 1:1 and MgCl₂ is 1:2.

Part 3 of 6Properties explained by the model

Property	Explanation
High melting and boiling points	Many strong electrostatic attractions need a lot of energy to overcome
Hard but brittle	Layers shift so like charges line up and repel, and the crystal splits with straight edges
No conduction as a solid	Ions are fixed in place
Conducts when molten or dissolved	Ions are free to move and carry charge
Often soluble in water	Water molecules attract the ions and pull them apart

Brittleness

Brittleness if a crystal is dropped it breaks between one row of ions and another, leaving pieces with straight edges.

Stronger attraction

Stronger attraction ions with double charges, as in magnesium oxide (Mg²⁺ and O^2-), attract more strongly than in sodium chloride.
Magnesium oxide melts at about 2850 °C compared with 801 °C for sodium chloride.

Insoluble compounds

Insoluble compounds some ionic compounds are insoluble because the attraction in the lattice is stronger than the attraction to water molecules.

Part 4 of 6Working out formulae

Rule

Rule the total positive charge must equal the total negative charge.

Examples

Ca²⁺ and Cl^- give CaCl₂, and Mg²⁺ and O^2- give MgO.

Part 5 of 6Dot-and-cross diagrams

Dot-and-cross diagrams

Draw the metal atom with its outer electrons and the non-metal atom with its outer electrons.

Show the electron moving from the metal to the non-metal with an arrow.

Draw each ion in square brackets with the charge at the top right outside the brackets.

Sodium chloride

Sodium chloride sodium loses its outer shell and is shown as 2,8 with 1+, and chlorine has eight outer electrons and 1-.

Magnesium chloride

Magnesium chloride one magnesium atom transfers an electron to each of two chlorine atoms, giving MgCl₂.

Quick check

Quick check the metal loses electrons, the non-metal gains them, and the charges balance in the formula.

Part 6 of 6Modelling ionic bonding

Model

Model an idea that explains observations and helps make predictions, and the giant ionic structure is a model.

Physical model

Barney and Sarah used grapes to model a giant ionic structure of sodium chloride.

Strength

Strength it shows the positions of the oppositely charged ions.

Limitations

Limitations it does not show that ions vibrate on the spot, how the attraction acts in all directions, or why ionic compounds are brittle.

Key terms

Term	Meaning
Ionic bond	the electrostatic attraction between oppositely charged ions.
Ionic compound	a compound made of positive and negative ions.
Giant ionic structure	a three-dimensional pattern of oppositely charged ions.
Lattice	a regular repeating arrangement of particles.
Brittle	breaking easily when hit.
Molten	melted; in the liquid state.