What Are Covalent Bonds

Learn the basics about covalent bonds, when learning about properties of matter. When similar atoms react, like non-metals combining with other non-metals, they share electrons. This is covalent bonding. Non-metals have shells of electrons that are normally half or more than half full of electrons. Since they have a strong attraction for a few additional electrons, it is energetically unfavourable for any of them to lose electrons, so they share electrons by overlapping orbitals. This makes a bonding orbital, or covalent bond, that contains two or more electrons. Covalent bonds can be represented by a dot and cross diagram. These diagrams show only the valence electrons. Covalent bonds are directional, which means they are in a fixed position. The overlap between orbitals mean that the atoms in covalent bonds are very close, and make covalent bonds strong. There are two kinds of covalent structure - small molecules, like water, and giant compounds, like diamond. The electrons in the bonds are evenly shared, which means the bonds are not polarised; there is little attraction between molecules, and forces between molecules are weak. Compounds made from small covalent molecules have low melting and boiling points and are volatile. They also don’t conduct electricity. Carbon and silicon tend to form giant covalent compounds. These bond in the same way, but instead of forming small molecules with one or two bonds, they form four, make up huge lattices or chains of many many linked up atoms. Diamond is a common example, and is made up of Carbon. These compounds have very high melting and boiling points because you have to break covalent bonds rather than intermolecular forces to make them free enough to act like liquids or gases. The covalent bonds hold them rigidly in place in the giant lattice.