Understanding the Valency of Aluminium Ion

To determine the valency of the aluminium ion, we need to look at its atomic structure and how it forms ions.

Step 1: Find the Atomic Number of Aluminium

The atomic number of aluminium (Al) is 13. This means it has 13 protons and, in a neutral atom, 13 electrons.

Step 2: Write the Electron Configuration

The electron configuration of aluminium is: $1s^{2}2s^{2}2p^{6}3s^{2}3p^1$

This shows that aluminium has 3 electrons in its outermost shell (the third shell: $3s^{2}3p^1$).

Step 3: Determine How It Forms a Stable Ion

Atoms gain or lose electrons to achieve a stable electron configuration, usually that of a noble gas. The nearest noble gas to aluminium is neon (Ne, atomic number 10).

To achieve this stable configuration, aluminium loses its 3 outermost electrons. This results in an ion with a charge of +3.

The formation of the aluminium ion can be represented as: $\mathrm{Al}\to \mathrm{Al}{}^{\mathrm{3+}}+3e^{-}$

Step 4: Relate Charge to Valency

The valency of an element is the combining capacity of its atoms. For ions, the valency is equal to the magnitude of the charge on the ion.

Since the aluminium ion has a charge of +3, its valency is 3. Therefore, the aluminium ion is trivalent.

Final Answer

Aluminium ion is trivalent.

Related Topics & Formulae

Key Concepts

• Valency: The combining power of an element, often determined by the number of electrons it needs to lose, gain, or share to complete its outer shell.
• Ion Formation: The process where an atom loses or gains electrons to form a charged particle (ion). Metals tend to lose electrons to form positively charged cations.
• Electron Configuration: The distribution of electrons of an atom in atomic orbitals. It is crucial for predicting an element's chemical properties.

Important Formulae & Representations

Ion Formation Equation: $M\to M{}^{n+}+n{e}^{-}$

Where $M$ is a metal atom and $n$ is its valency.