Electronegativity

Definition

Electronegativity is the tendency of an atom to attract electrons in a chemical bond, reflecting its ability to pull shared electrons toward itself. This property is crucial in understanding bond types, molecular polarity, and the reactivity of different elements. Electronegativity values help predict how atoms will interact during bonding, influencing the properties of compounds formed from elements across various groups of the periodic table.

5 Must Know Facts For Your Next Test

1. Electronegativity increases across a period in the periodic table due to increasing nuclear charge that pulls electrons closer to the nucleus.
2. Elements with low electronegativity, like alkali metals, tend to lose electrons easily, while high electronegativity elements like halogens readily attract electrons.
3. The Pauling scale is the most commonly used scale for measuring electronegativity, with values ranging typically from about 0.7 for cesium to 4.0 for fluorine.
4. When two atoms have significantly different electronegativities, the bond formed between them is likely to be ionic due to complete transfer of electrons.
5. In covalent bonds between atoms with different electronegativities, the electron density is unevenly distributed, resulting in polar molecules.

Review Questions

• How does the trend in electronegativity vary across periods and groups in the periodic table, and what implications does this have for bond formation?
  • Electronegativity generally increases from left to right across a period and decreases down a group in the periodic table. This trend means that elements on the right side, like halogens, are more likely to attract electrons compared to those on the left, like alkali metals. As a result, when elements with differing electronegativities form bonds, they can create ionic or polar covalent bonds depending on the magnitude of the difference in their electronegativities.
• Discuss how electronegativity influences molecular polarity and the physical properties of substances.
  • Electronegativity plays a critical role in determining molecular polarity. In a covalent bond between two atoms with differing electronegativities, the atom with higher electronegativity attracts the shared electrons more strongly, creating a dipole moment. This polarity affects various physical properties such as boiling and melting points, solubility, and reactivity. Molecules with polar bonds often interact strongly with each other and can dissolve well in polar solvents.
• Evaluate how understanding electronegativity can aid in predicting chemical reactivity and bond type for various elements.
  • Understanding electronegativity allows chemists to predict how different elements will react based on their tendencies to gain or lose electrons. For instance, knowing that fluorine has high electronegativity suggests it will readily form strong bonds with less electronegative elements like sodium, leading to ionic compounds. Additionally, this knowledge aids in anticipating how molecules will behave during chemical reactions, such as whether they will form covalent or ionic bonds and how they will interact with other substances.

Related terms

Ionization Energy: The energy required to remove an electron from an atom in its gaseous state, closely related to electronegativity as both involve an atom's ability to interact with electrons.

Electron Affinity: The amount of energy released when an atom gains an electron, providing insight into how likely an atom is to attract additional electrons.

Covalent Bonding: A type of chemical bond where atoms share pairs of electrons, with the degree of sharing influenced by the electronegativity of the bonded atoms.