Electronegativity

Definition

Electronegativity is a measure of an atom's ability to attract and hold onto electrons within a chemical bond. It plays a crucial role in determining the nature of chemical bonds, influencing molecular polarity, and affecting the behavior of molecules in various chemical reactions.

5 Must Know Facts For Your Next Test

1. Electronegativity values are often measured on the Pauling scale, where fluorine is the most electronegative element with a value of 4.0.
2. Differences in electronegativity between bonded atoms determine the type of bond formed: nonpolar covalent, polar covalent, or ionic.
3. Elements with high electronegativity tend to attract electrons more strongly, which can lead to polar covalent bonds when bonded with less electronegative elements.
4. The concept of electronegativity helps predict molecular geometry and reactivity by indicating how electron density is distributed within a molecule.
5. Changes in electronegativity across a period and down a group in the periodic table can be explained by atomic size and effective nuclear charge.

Review Questions

• How does electronegativity influence the type of chemical bond formed between two atoms?
  • Electronegativity influences the type of chemical bond by determining how electrons are shared or transferred between atoms. When two atoms have similar electronegativities, they typically form a nonpolar covalent bond by sharing electrons equally. If there is a moderate difference in electronegativity, a polar covalent bond is formed with unequal sharing of electrons. In cases where the difference is significant, an ionic bond occurs as one atom fully transfers electrons to another, leading to the formation of charged ions.
• Discuss how electronegativity contributes to the polarity of molecules and provide an example.
  • Electronegativity contributes to molecular polarity by creating an uneven distribution of electron density when atoms with different electronegativities bond. This leads to the development of partial positive and negative charges within the molecule. For example, in water (H₂O), oxygen has a higher electronegativity than hydrogen. As a result, the electrons are pulled closer to the oxygen atom, creating a polar molecule with a partial negative charge on the oxygen and partial positive charges on the hydrogens.
• Evaluate the impact of electronegativity on chemical reactivity and molecular structure in organic compounds.
  • Electronegativity significantly impacts chemical reactivity and molecular structure in organic compounds by influencing how molecules interact with one another. For instance, compounds containing functional groups like alcohols or carboxylic acids exhibit distinct reactivity patterns due to the presence of highly electronegative oxygen atoms. The polarity established by differences in electronegativity can affect reaction mechanisms, such as nucleophilic attacks or electrophilic additions. Moreover, understanding electronegativity helps chemists predict molecular geometry and potential sites for chemical reactions within organic compounds.

Related terms

Covalent Bond: A type of chemical bond where two atoms share pairs of electrons, often influenced by their electronegativities.

Polar Molecule: A molecule that has a net dipole moment due to the presence of polar bonds, which occur when atoms with different electronegativities bond together.

Ionic Bond: A type of chemical bond formed through the transfer of electrons from one atom to another, typically occurring between atoms with significantly different electronegativities.