Electronegativity is a measure of how strongly an atom attracts electrons to itself in a chemical bond. It is one of the most important properties of elements, as it affects their reactivity, bonding, and polarity. In this article, we will describe how electronegativity is related to the metallic character of an element, which is the tendency to lose electrons and form positive ions.
Contents
The Periodic Trend of Electronegativity
The electronegativity values of the elements are not constant, but vary according to their position in the periodic table. Generally, electronegativity increases from left to right across a period, and decreases from top to bottom down a group. This trend can be explained by the following factors:
- Atomic size: As the atomic size increases, the distance between the nucleus and the valence electrons increases, which reduces the attraction between them. Therefore, larger atoms have lower electronegativities than smaller atoms.
- Nuclear charge: As the nuclear charge increases, the attraction between the nucleus and the valence electrons increases, which increases the electronegativity. Therefore, atoms with higher atomic numbers have higher electronegativities than atoms with lower atomic numbers.
- Shielding effect: As the number of inner electrons increases, they shield the valence electrons from the full effect of the nuclear charge, which reduces the electronegativity. Therefore, atoms with more inner shells have lower electronegativities than atoms with fewer inner shells.
Based on these factors, we can predict that fluorine (F) has the highest electronegativity of all elements (4.0), and cesium (Cs) has the lowest electronegativity of all elements (0.7). The figure below shows a three-dimensional plot of the electronegativity values of the elements according to their position in the periodic table.
The Relationship between Electronegativity and Metallic Character
Metallic character refers to the level of reactivity of a metal. Metals tend to lose electrons easily and form positive ions (cations), which are attracted to negative ions (anions) in ionic compounds. Non-metals tend to gain electrons easily and form negative ions (anions), which are attracted to positive ions (cations) in ionic compounds. Therefore, metallic character is inversely related to electronegativity: as the electronegativity increases, the metallic character decreases; as the electronegativity decreases, the metallic character increases.
This relationship can be understood by considering the ionization energy and electron affinity of an element. Ionization energy is the amount of energy required to remove an electron from an atom in its gaseous state. Electron affinity is the amount of energy released when an electron is added to an atom in its gaseous state. Elements with high ionization energies tend to have high electronegativities, as they do not want to lose electrons. Elements with low ionization energies tend to have low electronegativities, as they want to lose electrons. Elements with high electron affinities tend to have high electronegativities, as they want to gain electrons. Elements with low electron affinities tend to have low electronegativities, as they do not want to gain electrons.
Therefore, we can conclude that elements with high electronegativities are more likely to form anions and exhibit non-metallic character, while elements with low electronegativities are more likely to form cations and exhibit metallic character.
Examples of Electronegativity and Metallic Character
To illustrate the relationship between electronegativity and metallic character, let us look at some examples of elements and compounds.
- Sodium (Na) has a low electronegativity of 0.9 and a high metallic character. It readily loses its one valence electron and forms a cation with a charge of +1 (Na+). Sodium reacts violently with water and forms sodium hydroxide (NaOH) and hydrogen gas (H2).
- Chlorine (Cl) has a high electronegativity of 3.2 and a low metallic character. It readily gains an electron and forms an anion with a charge of -1 (Cl-). Chlorine reacts with sodium and forms sodium chloride (NaCl), which is a common table salt.
- Carbon © has a moderate electronegativity of 2.6 and a variable metallic character. It can either lose or gain electrons depending on its bonding partner. Carbon can form covalent bonds with other non-metals, such as hydrogen (H), oxygen (O), nitrogen (N), etc., and form organic compounds, such as methane (CH4), carbon dioxide (CO2), ammonia (NH3), etc. Carbon can also form ionic bonds with some metals, such as calcium (Ca), iron (Fe), etc., and form carbides, such as calcium carbide (CaC2), iron carbide (Fe3C), etc.
Conclusion
Electronegativity is a measure of how strongly an atom attracts electrons to itself in a chemical bond. It varies according to the position of the element in the periodic table, and is influenced by the atomic size, nuclear charge, and shielding effect. Electronegativity is inversely related to the metallic character of an element, which is the tendency to lose electrons and form positive ions. Elements with high electronegativities tend to form anions and exhibit non-metallic character, while elements with low electronegativities tend to form cations and exhibit metallic character.
