For more recent data on covalent radii see Covalent radius. Irreversible antagonists bind via covalent intermolecular forces. Pairs of electrons located between atoms represent covalent bonds. Bonds with partially ionic and partially covalent character are called polar covalent bonds. Glycolipids are lipids with a carbohydrate attached by a glycosidic (covalent) bond. Ionic bonds may be seen as extreme examples of polarization in covalent bonds. Block copolymers comprise two or more homopolymer subunits linked by covalent bonds. Chemical bonds can be grouped into two types consisting of ionic and covalent. Polymer chains are connected via covalent bonds. Saturated hydrocarbons are hydrocarbons having only single covalent bonds between their carbons. This strength results from the covalent sp bonds formed between the individual carbon atoms. Transition metal complexes are generally bound by coordinate covalent bonds. The tetrafluorides show a mixture of ionic and covalent bonding. Maleimides selectively attach to cysteine using a covalent Michael addition. Compounds in which components share electrons are known as covalent compounds.