How do atoms achieve noble-gas configurations in single covalent bonds

Elements forming covalent compounds achieve noble gas configuration by sharing electrons within the atoms, unlike ionic compounds which achieve the noble gas configuration either by gaining or losing electrons from the outermost electron shell.

What are the options? physical property can be color, smell, opacity, viscosity, density, infra red spectrum, melting and boiling points, attraction and repulson to magnets, etc.