1.8 CHAPTER 1. ATOMICCOMBINATIONS
not contain one Na andone Cl ion, but rather alot of these two ions arranged in a crystal lattice where
the ratio of Na to Cl ions is 1:1. The structure ofa crystal lattice is shownin Figure 1.7.atom of element 1 (e.g.Na)atom of element 2 (e.g.Cl)ionic bonds hold atomstogether
in the lattice structure�
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��Figure 1.7: The crystal lattice arrangement in anionic compound (e.g. NaCl)Properties of Ionic Compounds ESBM
Ionic compounds have anumber of properties:- Ions are arranged in a lattice structure
- Ionic solids are crystalline at room temperature
- The ionic bond is a strong electrical attraction.This means that ionic compounds are often hard
and have high melting and boiling points - Ionic compounds are brittle, and bonds are broken along planes whenthe compound is stressed
- Solid crystals don’t conduct electricity, but ionic solutions do
1.8 Metallic bonds
ESBN
The nature of the metallic bond ESBO
The structure of a metallic bond is quite different from covalent and ionic bonds. In a metal bond,
the valence electrons are delocalised, meaning that an atom’s electrons do not stayaround that one
nucleus. In a metallicbond, the positive atomic nuclei (sometimes called the ’atomic kernels’) are
surrounded by a sea of delocalised electrons which are attracted to the nuclei (Figure 1.8).