Study Guides/Chemistry/Valency of Carbonate
Study Guide · Chemistry

What is the Valency of Carbonate?

In Class 9 Chemistry (Atoms and Molecules), learning how to write chemical formulas using the criss-cross method requires you to memorize the valency of various ions. The Carbonate ion is a very common polyatomic ion you will encounter frequently.

Question (Click to Flip)

What happens when you add an acid to a carbonate?

Answer

Whenever any acid (like HCl) reacts with any metal carbonate (like CaCO3), it causes a brisk effervescence (fizzing) and releases Carbon Dioxide (CO₂) gas.

Card 1 of 1 free previews

Key Facts

Carbonate compounds are generally insoluble in water. The major exceptions to this rule are Sodium Carbonate, Potassium Carbonate, and Ammonium Carbonate, which easily dissolve in water.

The Formula and Charge

  • Chemical Formula: CO₃ (One Carbon atom bonded to three Oxygen atoms).
  • Charge: It has an overall ionic charge of -2 (written as CO₃²⁻).

The Valency

The valency of an ion is numerically equal to the magnitude of its charge (ignoring the plus or minus sign). Therefore, the valency of Carbonate is 2.

Why is the charge -2?

To understand this, look at the individual valencies:

  • Carbon (C) wants to share 4 electrons (Valency +4).
  • Oxygen (O) wants to gain 2 electrons (Valency -2). Since there are 3 oxygen atoms, the total requirement is -6.
  • Mathematical total: (+4) + (-6) = -2. The group of atoms is short of 2 electrons to be completely stable, which is why the whole molecule carries a -2 charge.

Writing Formulas using Carbonate

Because Carbonate has a valency of 2, it will combine with two atoms of a metal with valency 1, or one atom of a metal with valency 2.

  • Sodium Carbonate (Washing Soda): Sodium (Na) has a valency of 1. By cross-multiplying, the formula becomes Na₂CO₃.
  • Calcium Carbonate (Chalk/Limestone): Calcium (Ca) has a valency of 2. Since both Calcium and Carbonate have a valency of 2, they cancel out. The formula is simply CaCO₃.

Questions and Answers

What happens when you add an acid to a carbonate?+

Whenever any acid (like HCl) reacts with any metal carbonate (like CaCO3), it causes a brisk effervescence (fizzing) and releases **Carbon Dioxide (CO₂) gas**.

More in Chemistry

⚗️

What are Transition Elements? Properties and Examples

Learn what transition elements are in Class 12 Chemistry. Understand their position in the periodic table, key properties, and important examples.

⚗️

Mnemonic Tricks to Learn d-Block Elements

Learn the easiest mnemonic tricks to memorize the 3d, 4d, and 5d series of the d-Block (Transition elements) in the Periodic Table for Class 11 and 12 Chemistry.

⚗️

Two Observations When Lead Nitrate is Heated

When lead nitrate is heated: (1) yellow residue of lead monoxide (PbO) forms; (2) brown fumes of nitrogen dioxide (NO₂) released. Balanced equation. Class 10 Chemistry.

⚗️

Two Synthetic Indicators

Two synthetic indicators used in Chemistry are Phenolphthalein and Methyl Orange. Learn their colour changes in acid and base with a comparison table. NCERT Class 10.

⚗️

Tyndall Effect — Definition, Cause and Examples

The Tyndall effect is the scattering of light by colloidal particles, making the beam of light visible. It distinguishes colloids from true solutions. Examples: fog, dusty rooms, forest sunlight.

Study Smarter with Shinyu.ai

Turn this guide into revision flashcards, a practice exam, or an AI-generated podcast — free, no signup required.