Metallic Bonds - Structure and Properties

A metallic bond involves two distinct parts: positive metal ions (formed when atoms lose outer electrons) and a sea of delocalised electrons that move freely throughout the structure.

The bond itself is the electrostatic attraction between the positively charged ion lattice and the negatively charged electron sea. This force acts in all directions (non-directional).

The option stating 'electrostatic attraction between a lattice of positive metal ions and a sea of delocalised electrons' includes all three required components: positive ions, delocalised electrons, and electrostatic attraction.

The question asks for the best description of a metallic bond, so we need the option that correctly names the particles and bonding force involved.

This describes a covalent bond, where electrons are shared between specific atom pairs. In metallic bonding, electrons are not localised between pairs — they are delocalised throughout the whole structure.

This describes an ionic bond. In metallic bonding, there are no fixed negative ions — instead there is a fluid sea of electrons, not discrete anions.

This describes van der Waals (London dispersion) forces, a type of intermolecular force. Metal atoms are not neutral in a metallic structure — they form positive ions.

The remaining option — electrostatic attraction between a lattice of positive metal ions and a sea of delocalised electrons — correctly describes metallic bonding with all key components.

Aluminium is in Group 13 of the periodic table. The group number tells us how many outer (valence) electrons the atom has.

In metallic bonding, each metal atom releases its outer electrons to the delocalised sea. Group 13 means aluminium has 3 outer electrons, so each Al atom contributes 3 electrons.

Each aluminium atom contributes 3 delocalised electrons, forming Al³⁺ ions in the lattice. The answer is 3.

The number of delocalised electrons per atom equals the number of outer (valence) electrons, which is given by the group number in the periodic table.

13 is the group number of aluminium in the periodic table, but this is not the number of outer electrons. Group 13 means 3 outer electrons (the 1 refers to the period, not the valence electrons in modern IUPAC notation).

1 delocalised electron per atom is typical of Group 1 metals like sodium. 2 is typical of Group 2 metals like magnesium. Aluminium is in Group 13 with 3 valence electrons, so neither 1 nor 2 is correct.

Aluminium (Group 13) has 3 outer electrons, contributing 3 delocalised electrons per atom to the electron sea, forming Al³⁺ ions.