The covalent radius (a measure of how large individual atoms are) shows different trends if you are moving across a period or down a group. A comparison of the relative covalent radii of atoms is ...

The higher an element's electronegativity ... with a large difference indicating a polar covalent bond (e.g., H-F bond) and a small difference indicating a non-polar covalent bond (e.g., C-C bond).

though they would likely be much weaker than traditional two-electron covalent bonds. While single-electron bonds have been ...

The properties of elements and compounds can be explained ... They can be broken down by electrolysis. All covalent network structures have very high melting points and boiling points.