🧪 Neutralization & salt structure
When acids neutralize bases or alkalis, salts and water are formed. For example, sodium hydroxide, an alkali, neutralizes hydrochloric acid to form sodium chloride and water. This reaction is called neutralization reaction.
NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
A salt is a chemical combination of positive and negative ions. These oppositely charged ions are then bonded together by the electrostatic force of attraction. The strength of this attraction depends on the magnitude of the charges and the distance between the ions.
These oppositely charged ions then arrange themselves in a regular and repeating pattern to give a three dimensional network structure called a crystal lattice. The properties shown by the ionic compounds are due to the presence of this ordered structure. Under ordinary conditions of temperature and pressure ionic compounds exist as crystalline solids.
Figure 18.1: Crystal lattice of sodium chloride (face-centered cube). Bigger chloride ions at corners and face centers; smaller sodium ions at edges.
Common salt was a valuable commodity in the past. It was even used as currency.
📝 10 MCQs · Ions in salts
📌 Notes & arrangement
In NaCl, each sodium ion is surrounded by six chloride ions and each chloride ion, in turn, is surrounded by six sodium ions. Figure 18.1 shows how these ions are arranged in the crystal lattice having the shape of a face-centered cube. The bigger chloride ions are present at the corners and at the centre of each face of the cube while the smaller sodium ions occupy the edges of the cube.
⚡ Electrostatic force depends on charge magnitude and distance.
🧠 Memorization tips
• NaCl lattice: “Cl at corners & faces, Na at edges” — think “big chloride (anion) occupies big positions: corners+faces; sodium small fills edges.”
• Neutralization: Acid + Base → Salt + Water (example: NaOH + HCl → NaCl + H₂O).
• Charges: NaCl: Na⁺ Cl⁻ ; each Na surrounded by 6 Cl (octahedral).
• Historical fact: Salt was currency — so remember “salt pays the ions”.
📅 Lesson planner · ions in salts
🎯 Guidelines for students
• Focus on the geometry: fcc unit cell of NaCl. Sketch it.
• Remember “opposites attract” – electrostatic force binds lattice.
• Ionic compounds exist as crystalline solids due to regular pattern.
• Connect real world: common salt (NaCl) was once currency.
• Attempt quiz without notes first, then check key.
• Use planner to track progress.