Question

Which among the following statements is false? (1) Pauling electronegativity scale is based on the experimental value of bond energies. (2) Electronegativity is a measure of the capacity of an atom to attract shared pair of electrons. (3) The atom with high electronegativity generally has high ionisation potential. (4) The electronegativity difference between the atoms gives an idea about bond length.

Short answer

Statement 4 is false.

Step-by-step solution

- Understand Electronegativity

Electronegativity is the tendency of an atom to attract a shared pair of electrons towards itself. The most commonly used electronegativity scale is the Pauling scale.

- Evaluate Statement 1

Pauling electronegativity scale is based on the differences in bond energies. So, statement 1 is true.

- Evaluate Statement 2

Electronegativity is indeed the measure of the capacity of an atom to attract shared pair of electrons. Thus, statement 2 is true.

- Evaluate Statement 3

Atoms with high electronegativity usually have high ionization potential, as both properties depend on the nuclear charge and the distance of the valence electrons from the nucleus. Therefore, statement 3 is true.

- Evaluate Statement 4

The electronegativity difference between atoms indicates the type of bond (ionic or covalent) and bond polarity, but it doesn't directly determine bond length. Hence, statement 4 is false.

Key concepts

Pauling scale

Electronegativity is a critical concept in chemistry that describes how strongly an atom attracts a pair of shared electrons in a bond. The Pauling scale, developed by Linus Pauling, is the most widely used method to quantify electronegativity. It's based on bond energies.
According to Pauling, the difference in bond energies between homonuclear (same atoms) and heteronuclear (different atoms) bonds can be used to calculate electronegativity values.
This means the Pauling scale isn't arbitrary; it corresponds to real, measurable properties of atoms.
Typically, electronegativity values range from around 0.7 for elements like francium to around 4.0 for fluorine, the most electronegative element.
The higher the value, the stronger the ability of the atom to attract electrons.

Key Points to Remember:

• The Pauling scale uses bond energy differences.
• This scale provides a numerical way to compare different elements.
• High values indicate strong electron attracting power.
• It's based on experimental data, making the scale reliable.

bond energies

Bond energy is a central concept in understanding electronegativity and chemical bonding.
It refers to the amount of energy needed to break one mole of bonds in a substance in the gas phase.
In simpler terms, bond energy is a measure of bond strength in a chemical bond.
When comparing bond energies, higher energy implies a stronger, more stable bond.
Bond energies are vital for several reasons:

• They help determine reaction feasibility: Reactions that release more energy are generally more favorable.
• They help calculate heats of formation and combustion.
• In the Pauling scale, they help calculate the differences in electronegativity between atoms.

For example, the bond energy of the H-H bond in hydrogen is different from the energy in a H-F bond, where F is highly electronegative.
This difference helps to derive the electronegativity values used in the Pauling scale.

ionization potential

Ionization potential, also known as ionization energy, is the energy required to remove an electron from an atom or ion in its gaseous state.
It's a measure of how strongly an atom holds onto its electrons. An atom with a high ionization potential does not easily lose electrons, showing it has a strong hold over them.
Generally, atoms with high electronegativity have high ionization potentials because both properties are influenced by similar factors:

• Nuclear charge: The more positively charged the nucleus, the stronger the pull on electrons.
• Distance of valence electrons from the nucleus: Electrons closer to the nucleus are held more tightly.

These factors make the relationship between electronegativity and ionization potential almost directly proportional.
For example, fluorine has both a high electronegativity and a high ionization potential, reflecting its strong nuclear charge and small atomic radius.