covalent bond
You have learned that a covalent bond forms when the electron clouds of two atoms overlap with each other. In a simple H 2 molecule, the single electron in each atom becomes attracted to the nucleus of the other atom in the molecule as the atoms come closer together. An optimum distance, equal to the bond length, is eventually attained, and the potential energy reaches a minimum. A stable, single covalent bond has formed between the two hydrogen atoms. Other covalent bonds form in the same way as unpaired electrons from two atoms match up to form the bond. In a fluorine atom, there is an unpaired electron in one of the 2p orbitals. When a F 2 molecule forms, the 2p orbitals from each of the two atoms overlap to produce the FF covalent bond. The overlapping orbitals do not have to be of the same type. In a molecule of HF, the 1s orbital of the hydrogen atom overlaps with the 2p orbital of the fluorine atom see Figure below .