Chapter 4: Unit 4. Formula of an ionic compound

Formula of an ionic compound

Cations and anions always form ionic compounds that have zero overall charge.

Ionic compound s are written with the cation first, and then the anion with subscript to show how many of each are needed to have zero net charge.  Ionic compounds are always written with lowest possible ratio between the atoms to form neutral compound.

In short, when the charges are unequal and opposite, ionic compound is formed by switching the opposite charges. When charges are equal and opposite, ionic compounds are formed by simply writing metal followed by nonmetal symbol.

Example:  Mg²⁺ + S^2-    → MgS

Al³⁺ + Cl^–    → AlCl₃

Pb ²⁺ + N³–   →  Pb₃N₂

Cations and anions always form ionic compounds that have zero overall charge.

Ionic compound s are written with the cation first, and then the anion with subscript to show how many of each are needed to have zero net charge.  I

onic compounds are always written with lowest possible ratio between the atoms to form neutral compound.

In short, when the charges are unequal and opposite, ionic compound is formed by switching the opposite charges. When charges are equal and opposite, ionic compounds are formed by simply writing metal followed by nonmetal symbol.

Example:  Mg²⁺ + S^2-    → MgS

Al³⁺ + Cl^–    → AlCl₃

Pb ²⁺ + N³–   →  Pb₃N₂

Cations and anions always form ionic compounds that have zero overall charge.

Ionic compound s are written with the cation first, and then the anion with subscript to show how many of each are needed to have zero net charge.  I

Ionic compounds are always written with lowest possible ratio between the atoms to form neutral compound.

Questions

Write the formula for the ionic compound formed from each pair of elements a) Barium and Bromine b) aluminum and sulfur c) zinc and sulfur d) magnesium and fluorine

Ans: a) BaBr₂ b) Al₂S_3, c) ZnS, d) MgF₂