Electronegativity Overview
Electronegativity is a feature of an atom that rises with its attraction to the electrons of a bond. In a covalent bond, two joined atoms with the same electronegativity values share electrons equally. In most chemical bonds, the electrons are more attracted to one atom (the more electronegative one) than to the other. This produces a polar covalent bond. If the electronegativity levels are extremely dissimilar, the electrons are not exchanged at all. An ionic bond is formed when one atom accepts the bond electrons from the other atom.
What is Electronegativity?
Electronegativity is the tendency of an atom in a molecule to draw the shared pair of electrons towards itself. Because it is merely a tendency, it is a dimensionless attribute. It essentially denotes the net effect of atoms in various elements' proclivity to attract bond-forming electron pairs. Electronegativity is measured on different scales. Linus Pauling created the most widely used scale.
Examples of Electronegativity
Because the chlorine atom has a higher electronegativity than the hydrogen atom, the bonding electrons in the HCl molecule will be closer to the Cl than to the H. Both atoms in the O2 molecule have the same electronegativity. The two oxygen atoms share the electrons in the covalent bond evenly.
History of Electronegativity
Before Jöns Jacob Berzelius called electronegativity in 1811, Avogadro and other scientists investigated it. Linus Pauling suggested an electronegativity scale based on binding energies in 1932. On the Pauling scale, electronegativity values range from around 0.7 to 3.98. The values on the Pauling scale are related to the electronegativity of hydrogen (2.20). Other scales, in addition to the Pauling scale, are the Mulliken scale, the Allred-Rochow scale, the Allen scale, and the Sanderson scale. Electronegativity is a characteristic of an atom inside a molecule, not a quality of an atom in and of itself. As a result, electronegativity fluctuates depending on an atom's surroundings. However, most of the time, an atom behaves similarly in diverse settings. Nuclear charge, as well as the quantity and placement of electrons in an atom, are all factors that influence electronegativity.
Most and Least Electronegative Elements
On the periodic chart, fluorine is the most electronegative element. It has an electronegativity of 3.98. Cesium is the element with the lowest electronegative potential. It has an electronegativity of 0.79. Because electro-positivity is the polar opposite of electronegativity, Cesium is the most electropositive element. The most electronegative elements are those that require only a few electrons to complete their valence shells and have the fewest number of inner electron shells between the positive nucleus and the valence electrons.
Impact of Electronegativity on Covalent Bonding
The strength of a covalent bond is greatly reliant on the electronegativities of the two bound atoms (particularly the difference in electronegativities). Because the electronegativities of the bound atoms are the same (resulting in the bonded pair of electrons being practically equidistant from the two bonded nuclei), homonuclear diatomic molecules have relatively 'pure' covalent connections. H2 molecules, Cl2 molecules, and O2 molecules are all examples of covalent bonding. Simultaneously, the more electropositive atom acquires a partial positive charge (denoted by +). The polarity of the chemical bond is determined by these partial charges.
Factors Affecting Electronegativity
The following are some of the factors that affect electronegativity-
Nuclear Charge
A higher nuclear charge value equals a higher electronegativity value. This occurs because an increase in nuclear charge creates stronger electron attraction.
Size of an Atom
A larger atomic size results in a lower value of electronegativity because electrons far out from the nucleus feel less force of attraction.
Substituent Effect
The electronegativity of an atom is determined by the type of substituent attached to that atom. For example, the carbon atom in CF3I receives a higher positive charge than the carbon atom in CH3I. As a result, the C-atom in CF3I is more electronegative than the C-atom in CH3I. The variation in electronegativity of an atom produced by substituents leads to a change in its chemical behavior.
Periodic Trends in Electronegativity of Elements
As we pass over a period in the contemporary periodic table from left to right, the nuclear charge increases and the atomic size decreases, hence, the value of electronegativity increases. In the current periodic chart, the atomic number increases as we proceed down the group. The nuclear charge likewise rises, but the effect of the rise is mitigated by the addition of one shell. As a result, we travel down the group, and the value of electronegativity diminishes. In the halogen group, for example, as we proceed down the group from fluorine to astatine, the electronegativity value falls. Metals have lower electronegativity values than nonmetals, which is a widespread finding. As a result, metals are electropositive while nonmetals are electronegative. Period two elements vary from their respective group elements in terms of attributes due to their tiny size and greater electronegativity value. The elements in the second period are similar to the elements in the third phase. This is caused by a little discrepancy in their electronegativities. As a result, a diagonal connection is formed.
Read more about the Reactivity Series of Metals.
Electronegativity Table
Electronegativity is a chemical characteristic that defines an atom's ability to pull shared-pair electrons toward itself in a molecule. There is a significant variation in electronegativity between elements on the left and right sides of the periodic table. The periodic chart of elements is shown below, along with the electronegativity table-
Points to Remember
- Electronegativity is the tendency of an atom in a chemical bond to attract electrons to itself.
- Fluorine is the most electronegative element. Francium is the least electronegative or most electropositive element.
- The bigger the difference in electronegativity values between atoms, the more polar the chemical connection formed between them.
Sample Questions Related to Electronegativity
Sample Question 1: Is electronegativity a conditional concept?
Solution: Electronegativity is an atom's capacity to attract electrons. It is proportional to the difference in ionization potential and electron attraction of an atom.
Sample Question 2: Which of the following groups is the least electronegative?
Solution: The alkali metals are unquestionably the least electronegative, with the least nuclear charge for a given time and the least shielding by other electrons (their valence shells contain only one electron). VIII, the inert gas, is the least electronegative group.
Sample Question 3: What is the IUPAC name and symbol for the atomic number 120 element?
Solution: The roots for 1, 2, and 0 are un, bi, and nil, respectively. As a result, the sign and term are Ubn and unbinilium, respectively.
Sample Question 4: Which of the following is the best definition of electronegativity?
Solution: Electronegativity is the capacity of an atom to attract an electron's binding pair. It is most typically measured using a Pauling scale. Fluorine has a value of 4.0, whereas cesium and francium are the least electronegative elements with values of 0.7.
Sample Question 5: What is the electronegativity calculation formula?
Solution: Subtract the smaller electronegativity from the greater one to discover the difference. If we consider the molecule HF, we would subtract hydrogen's electronegativity (2.1) from fluorine's (4.0). 1.9 = 4.0 - 2.1
Sample Question 6: What is the distinction between electronegativity?
Solution: Electronegativity describes how much an atom draws electrons in a chemical interaction. If the difference in electronegativity is more than 1.7, the bond will be ionic. If the difference in electronegativity is between 0.4 and 1.7, the bond is polar covalent.
Sample Question 7: How would you explain the occurrence of 18 elements in Period 5 of the Periodic Table?
Solution: When n equals 5, l equals 0, 1, 2, 3. The energy of the accessible orbitals 4d, 5s and 5p grows in the following order: 5s 4d 5p.
There are a total of nine orbitals accessible. The greatest number of electrons that may be accommodated is 18, hence the 5th period has 18 elements.