Electronegativity Chart

Introduction

Electronegativity can be described as the capability of an atom (inside a molecule) to attract (force) the electrons (shared ones) towards itself at the time of bond formation. The electronegativity of an atom can be affected (varies) by its atomic number (Z) and, also the distance from where the valence electrons stay or are found to be present in the charged nucleus. Electronegativity is useful in the estimation of the bond energy. Electronegativity for an element can be determined with the help of some scales like the Mulliken scale, polling scale, and Allred Roschow’s scale.

A polling scale is used to find the electronegativity difference between any two elements. While Allred Roschow’s scale is used to find the electronegativity of an atom. The electronegativity chart or table shows the elements present on the right top side (r-t) of the periodic table (p.t) are more or most (maximum) electronegative and the elements at the bottom are less electronegative. Hence, Fluorine is the most (maximum) electronegative and caesium is the least (minimum) electronegative element.

Introduction to Electronegativity

Electronegativity can be represented by the symbol (ꭙ). And it is defined or described as the capability of an atom to attract the electrons (shared) towards itself at the time of bond formation (chemical bond). Electronegativity is useful in the estimation of bond energy (B.E.) and the sign (‘+’ or ‘-’) and magnitude (numeric) of the bond’s chemical polarity. Electronegativity can be estimated by some factors like nuclear charge (actual positive charge), the number (no.) of electrons present in the atomic shell, on the location of other electrons, present inside the shell (atomic).

Electronegativity is not s specific property of any individual atom, but it is the property of an atom present inside the molecule. So, the electronegativity of an atom in a molecule is related (strongly) to the first ionization energy and related (negatively) to the electron affinity. Then, there comes a term called group electronegativity or substituent electronegativity. And this factor is also responsible for affecting the electronegativity of an atom in the molecule.

Sandbh, Electronegativity bars, CC BY-SA 4.0

What is Electronegativity?

Electronegativity can be expressed or denoted by the symbol (ꭙ). And it is defined or described as the capability of an atom to attract the electrons (shared) towards itself at the time of bond formation (chemical bond). Electronegativity can be estimated by some factors like nuclear charge (actual positive charge), the number (no.) of other electrons present in the atomic shell, and the location of other electrons, present inside the shell (atomic). Electronegativity is useful in the estimation of bond energy (B.E.) and the sign (‘+’ or ‘-’) and magnitude (numeric) of the bond’s polarity (chemical). Electronegativity is not a specific property of any individual atom, but it is the property of an atom present inside the molecule. Therefore, the electronegativity of an atom in a molecule is related (strongly) to the first ionization energy (I.E.) and related (negatively) to the electron affinity. The Electronegativity of an atom in the molecule can also be affected by group electronegativity or substituent electronegativity.

Factors affecting Electronegativity of an Atom (Element)

There are two factors affecting (vary) the electronegativity (ꭙ) of an atom (element) −

• Atomic number − The electronegativity (ꭙ) of an atom (inside a molecule) is directly proportional (∝) to the number (no.) of protons present in the nucleus. So, if the no. of protons presents inside the nucleus increases, the electronegativity also increases and vice-versa.

• Distance between the valence electrons and the nucleus − Larger the distance between the valence electrons and the nucleus or we can say that the larger the atomic size, the lesser will be the value of electronegativity and vice-versa.

Determination of Electronegativity of an Element

There are different types of scales used for calculating the electronegativity of an element.

• Pauling scale − Pauling scale is completely based on the empirical relationship between the energy of the bond and the electronegativity of the bonded atoms. And the equation for this is given by − $$\mathrm{ E_{A-B}>\sqrt{E_{A-A}×E_{B-B}}}$$

• Mulliken scale − Mulliken scale takes the average of ionization potential and the electron affinity called electronegativity. This can be represented by −

  $$\mathrm{\frac{Ionization potential+electron affinity}{2}}$$

• Allerd-Rochow scale − This scale is used to determine the values of the forces (electrostatic) exerted by the effective nuclear charge present on the valence electrons. And this force occurs on the surface of the atoms.

Electronegativity Chart and Electronegativity Trend in Periodic Table

• Electronegativity chart or table − As we know, electronegativity is the capability of an atom (individual) to attract the shared pairs of an atom or group of atoms. There is a huge electronegativity difference between the atoms found on the left-hand side and the atoms present on the right-hand side of the periodic table (p.t). Electronegativity is also very important or useful in determining the types of bonds between the elements and this is also considered one of the important factors in chemical bonding. And, as we know the electronegativity of an atom increases when we move towards the right (r) in the periodic table (p.t), also its electronegativity increases when we move up in the periodic table. So, the atoms present at the top right (t-r) of the periodic table have the highest electronegativities and the atoms present at the bottom left (b-l) of the table have the lowest electronegativities.

• Electronegativity trend in the periodic table − Generally, electronegativity decreases down the group and increases on moving from left (l) to right (r) along a period. So, it is found that fluorine(F) has the highest (maximum) electronegativity in the periodic table and, caesium has the least or minimum electronegativity in the same periodic table. Therefore, the compound called caesium fluoride has the most (maximum) ionic character. Although there are certain exceptions and those are gallium (Ga) and germanium (Ge). Since, they have higher (more) electronegativities than aluminium (Al) and, silicon (Si) respectively. This is due to the d-block or d-orbital contraction. Also, the elements of the fourth (4th) period, just after the first (1st) row of the transition type metals have abnormally smaller atomic radii this is again due to the d-orbital contraction. That means here the 3d-electrons (e^-) are not effective or capable of shielding or covering the increased (exceeded) nuclear charge and as we know smaller size correlates or relates with higher electronegativity. One another abnormality is the high electronegativity of lead (Pb) as compared to thallium (Th) and bismuth (Bi).

Electronegativity trends in transition metals

Transition metals are the elements present in the group range 3 (three) to 12 (twelve) in the periodic table and, these are generally identified by partially (half) filled d subshells. And the electronegativity of the transition elements increases from left (l) to right (r) and from the top (t) to bottom (b) in the d-block. Although due to the free-flowing of outer d-orbital electrons, transition metals have low electronegativity.

Conclusion

Electronegativity can be expressed or denoted by the symbol (ꭙ). And it is defined or described as the capability of an atom to attract the electrons (shared) towards itself at the time of bond formation (chemical bond). Electronegativity can be estimated or calculated by some factors like nuclear charge (actual positive charge), the number of other electrons present in the atomic shell, and the location of other electrons, present inside the shell (atomic). Electronegativity is useful in the estimation of bond energy (B.E.) and the sign (‘+’ or ‘-’) and magnitude (numeric) of the bond’s chemical polarity. Electronegativity is not a specific property of any individual atom, but it is the property of an atom present inside the molecule. The electronegativity of an atom can be affected (varies) by its atomic number(Z) and the distance (d) between the valence electrons and the charged nucleus.

FAQs

1. What do you mean by electronegativity?

Electronegativity is defined as the capability of an atom present inside the molecule to attract the shared electrons towards itself at the time of bond formation.

2. What is the Electronegativity chart?

The electronegativity chart is the representation of the elements in the table according to their electronegativity values. Generally, electronegativity increases when we move from left (l) to right (r)along a period and reduces when we move top (t) to bottom (b) or down (below) a group.

3. Who has developed the electronegativity chart?

Linus Pauling created or developed the electronegativity chart.

4. What is the Pauling scale used for?

The Pauling scale is used to determine the electronegativity of the atoms (bonded ones). This scale expresses the empirical relationship between the bond energy and electronegativity.

5. What is the basic difference between the Pauling scale and the Mulliken scale?

The Pauling scale is used to determine the electronegativity of the atoms in the molecules while the Mulliken scale is used to determine the electronegativity of individual atoms.