electronegativity

Examples of electronegativity in the following topics:

• Electronegativity and Oxidation Number

  • An atom's electronegativity is affected by both its atomic number and the size of the atom.
  • The higher its electronegativity, the more an element attracts electrons.
  • The most commonly used method of calculation for electronegativity was proposed by Linus Pauling.
  • Hence, fluorine (F) is the most electronegative of the elements, while francium (Fr) is the least electronegative.
  • Electronegativity is highest at the top right of the table and lowest at the bottom left.

• Bond Polarity

  • One atom might exert more of a force on the electron cloud than the other; this pull is called electronegativity.
  • Electronegativity measures a particular atom's attraction for electrons.
  • Atoms with high electronegativity values—such as fluorine, oxygen, and nitrogen—exert a greater pull on electrons than do atoms with lower electronegativity values.
  • A completely nonpolar bond occurs when the electronegativity values are identical and therefore have a difference of zero.
  • The more electronegative (4.0 > 2.1) fluorine pulls the electrons in the bond closer to it, forming a partial negative charge.

• Hydrogen Bonding

  • A hydrogen bond is the electromagnetic attraction created between a partially positively charged hydrogen atom attached to a highly electronegative atom and another nearby electronegative atom.
  • A hydrogen atom attached to a relatively electronegative atom is a hydrogen bond donor.
  • This electronegative atom is usually fluorine, oxygen, or nitrogen.
  • Greater electronegativity of the hydrogen bond acceptor will create a stronger hydrogen bond.
  • Ethanol contains a hydrogen atom that is a hydrogen bond donor because it is bonded to an electronegative oxygen atom, which is very electronegative, so the hydrogen atom is slightly positive.

• Charge Distribution in Molecules

  • The ability of an element to attract or hold onto electrons is called electronegativity.
  • Fluorine has the greatest electronegativity of all the elements, and the heavier alkali metals such as potassium, rubidium and cesium have the lowest electronegativities.
  • It should be noted that carbon is about in the middle of the electronegativity range, and is slightly more electronegative than hydrogen.
  • When two different atoms are bonded covalently, the shared electrons are attracted to the more electronegative atom of the bond, resulting in a shift of electron density toward the more electronegative atom.
  • Electronegativity differences may be transmitted through connecting covalent bonds by an inductive effect.

• Dipole Moment

  • The atom with larger electronegativity will have more pull for the bonded electrons than will the atom with smaller electronegativity; the greater the difference in the two electronegativities, the larger the dipole.
  • This is the case when both atoms' electronegativity is the same.
  • For example, a molecule of carbon dioxide has two carbon—oxygen bonds that are polar due to the electronegativity difference between the carbon and oxygen atoms.
  • KBr has one of the highest dipole moments because of the significant difference in electronegativity between potassium and bromine.

• Alkyl Halide Reactions

  • With the exception of iodine, these halogens have electronegativities significantly greater than carbon.
  • Two characteristics other than electronegativity also have an important influence on the chemical behavior of these compounds.
  • The second factor to be considered is the relative stability of the corresponding halide anions, which is likely the form in which these electronegative atoms will be replaced.

• Oxidations & Reductions

  • To determine whether a carbon atom has undergone a redox change during a reaction we simply note any changes in the number of bonds to hydrogen and the number of bonds to more electronegative atoms such as O, N, F, Cl, Br, I, & S that has occurred.
  • If the number of hydrogen atoms bonded to a carbon increases, and/or if the number of bonds to more electronegative atoms decreases, the carbon in question has been reduced (i.e. it is in a lower oxidation state).
  • If the number of hydrogen atoms bonded to a carbon decreases, and/or if the number of bonds to more electronegative atoms increases, the carbon in question has been oxidized (i.e. it is in a higher oxidation state).
  • Since metals such as lithium and magnesium are less electronegative than hydrogen, their covalent bonds to carbon are polarized so that the carbon is negative (reduced) and the metal is positive (oxidized).

• Periodic Trends in Metallic Properties

  • When two elements are joined in a chemical bond, the element that attracts the shared electrons more strongly has more electronegativity.
  • Elements with low electronegativity tend to have more metallic properties.
  • These elements all possess low electronegativities and readily form positive ions.

• Introduction to Bonding

  • The nature of the interaction between the atoms depends on their relative electronegativity.
  • Atoms with equal or similar electronegativity form covalent bonds, in which the valence electron density is shared between the two atoms.
  • When there is a greater electronegativity difference than between covalently bonded atoms, the pair of atoms usually forms a polar covalent bond.
  • Finally, for atoms with the largest electronegativity differences (such as metals bonding with nonmetals), the bonding interaction is called ionic, and the valence electrons are typically represented as being transferred from the metal atom to the nonmetal.

• Comparison between Covalent and Ionic Compounds

  • These bonds mostly occur between nonmetals or between two of the same (or similar) elements.Two atoms with similar electronegativity will not exchange an electron from their outermost shell; the atoms instead share electrons so that their valence electron shell is filled.
  • Ionic bonding occurs when there is a large difference in electronegativity between two atoms.
  • This large difference leads to the loss of an electron from the less electronegative atom and the gain of that electron by the more electronegative atom, resulting in two ions.