electronegativity


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electronegativity

(ĭlĕk'trōnĕgətĭv`ətē), in chemistry, tendency for an atom to attract a pair of electrons that it shares with another atom (see chemical bondchemical bond,
mechanism whereby atoms combine to form molecules. There is a chemical bond between two atoms or groups of atoms when the forces acting between them are strong enough to lead to the formation of an aggregate with sufficient stability to be regarded as an
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). For example, the molecule hydrogen chloride, HCl, consists of a hydrogen atom, H, and a chlorine atom, Cl, sharing a pair of electrons. If the pair of electrons are not shared equally, i.e., if they spend more time with one atom than with the other, the favored atom is said to be more electronegative. In the case of HCl, measurements indicate that the molecule has a dipole moment, that is, the chlorine end is relatively negative and the hydrogen end is relatively positive. This means that the electron pair spends more time with the chlorine atom than with the hydrogen atom and thus chlorine is more electronegative than hydrogen. Nonmetals have much higher electronegativities than metals; of the nonmetals, fluorine is the most electronegative, followed by oxygen, nitrogen, and chlorine. The larger the difference in electronegativity between two atoms, the more polar the bond between them. In the extreme case of a bond between a metal and a nonmetal, a complete transfer of electrons takes place.

Electronegativity

 

a quantity that characterizes the power of an atom in a molecule to attract electrons that take part in the formation of chemical bonds. Several methods have been developed for the calculation of electronegativity. For example, in 1935, R. Mulliken suggested that the sum of an atom’s ionization potential and electron affinity could serve as a measure of the atom’s electronegativity. In 1932, L. Pauling proposed another, more complicated method (seeCHEMICAL BOND). However, all the known methods turn out to yield virtually identical results.

If electronegativities are known, the electron density distribution in the molecules of many chemical substances may be approximately estimated. For example, the polarity of a covalent bond can be determined.

References in periodicals archive ?
The importance of the electronegativity concept and the graph are strongly emphasized as vital for understanding chemical bonding and the other principles that are described later, and is referred to again repeatedly as each chemical concept is explained.
Parr, who has developed a rival method for deriving electronegativity values, says the scientific community will eventually decide which definition of electronegativity reveals the most about chemical bonding.
2005) mention that the incorporation of PVC improves thermo-oxidative stability of NBR towards ozone or other oxidative atmosphere due to the electronegativity of chlorine atoms.
On the other hand, the greater electronegativity, smaller size, and coordination of the nitrate ion implies its lesser affinity to sorption (compared with phosphate on a given site) at identical concentrations to phosphate.
It is, however, complicated by the electronegativity of oxygen.
Derivatization with S-HFBPCl led to AM and/or MA derivatives that were readily ionized in the NICI ionization mode because of the electronegativity of the heptafluorobutyryl moiety (39).
Their unique combination of properties derives from the high strength of the C-F bond (116 kcal) and the high electronegativity of fluorine.
This research complements the group's investigations of the topological properties of the electron density distributions of molecules and the relationships between the topological properties and chemical concepts, such as bond order, electronegativity, hydrogen bonding and transition states.
For anions on the polymer network, according to the calculating method of the group's electronegativity, --S[O.