Different theorists have different categorizations and conceptualizations of defense mechanisms. Large reviews of theories of defense mechanisms are available from Paulhus, Fridhandler and Hayes (1997) and Kramer (1991). The Journal of Personality published a special issue on defense mechanisms (1998). In the first definitive book on defense mechanisms, The Ego and the Mechanisms of Defense (1936), Anna Freud enumerated the ten defense mechanisms that appear in the work of her father, Sigmund Freud, that included: repression, regression, reaction formation, isolation, undoing, projection, introjection, turning against one's own person, reversal into the opposite, and sublimation or displacement. Sigmund Freud posited that defense mechanisms work by distortimg id impulses into acceptable forms, or by unconscious or conscious blockage of these impulses. Anna Freud considered defense mechanisms as intellectual and motor automisms of various degrees of complexity, that arose in the pr

 A chemical bond is a lasting attraction between atoms, ion, or molecules that enables the formation of chemical compounds. The bond may result from the electrostatic force between opposite charged ions as in ionic bonds or through the sharing of electrons as in covalent bonds. The strength of chemical bonds varies considerably; there are "strong bonds" or "primary bonds" such as ionic, covalent, and metallic bonds, and "weak bonds" or "secondary bonds" such as dipole-dipole interactions, the London dispersion force, and hydrogen bonding. Since opposite charges attract via a simple electromagnetic force, the negatively charged electrons orbiting the nucleus and the positively charged protons in the nucleus attract each other. An electron positioned between two nuclei will be attracted to both of them, and the nuclei will be attracted toward electrons in this position. This attraction constitute chemical bond. Due to the matter wave nature of elec