Pure covalent bonds
A covalent bond is a shared pair of electrons, electrostatically attracted to the positive nuclei of two atoms.
Atoms can share electrons in order to achieve a stable outer electron arrangement (a noble gas arrangement).
Pure covalent bonds exist between two atoms with the same electronegativities. A pure covalent bond has no ionic character at all.
Diatomic elements are good examples of pure covalent bonds where the electrons are evenly shared between both nuclei.