Question Video: Determining Which Alkali Metal Is the Least Electronegative | Nagwa Question Video: Determining Which Alkali Metal Is the Least Electronegative | Nagwa

# Question Video: Determining Which Alkali Metal Is the Least Electronegative Chemistry • Second Year of Secondary School

## Join Nagwa Classes

By considering the Pauling scale, used to quantify electronegativity, which of the following elements is the least electronegative? [A] Cs [B] Na [C] Rb [D] K [E] Li

02:58

### Video Transcript

By considering the Pauling scale, used to quantify electronegativity, which of the following elements is the least electronegative? (A) Cesium, (B) sodium, (C) rubidium, (D) potassium, or (E) lithium.

Electronegativity values describe the tendency of an atom to withdraw electron density from a chemical bond. Electron density tends to be higher around the bonded atom that has the higher electronegativity number. The figure shows how electron density is higher about the more electronegative atom of a covalent bond. While many scientists have devised methods for quantifying electronegativity numbers, all of the proposed methods generate similar numbers.

Linus Pauling proposed a very famous method for determining the electronegativity number of elements. This method determines electronegativity numbers from bond dissociation data, which is the energy data obtained when measuring the dissociation of a covalent bond. Scientists have determined the Pauling electronegativity number for most of the chemical elements. And this figure shows these numbers for the listed alkali metals.

The numbers become smaller as we move from the top of the group to the bottom, and we can understand the trend of electronegativity numbers if we consider the relationship between atomic size and electronegativity. Atoms effectively withdraw a lot of electron density if they are small because their positively charged protons are close to the electrons of the bond. Larger atoms are less effective at withdrawing electron density because their protons are further apart from the electrons of the chemical bond. And so, there is a relatively weak force of attraction between the atomic nucleus of a large atom and the electrons of its bond.

Atomic radius, which we typically use to represent atomic size, tends to increase with atomic number. Since the atomic radius becomes increasingly large down a group in the periodic table, these larger atoms will have a weaker interaction with the electrons of the bond. The element cesium has the highest atomic number of all the listed alkali metals. It is close to the bottom left of the periodic table and has a larger diameter than all the other listed elements. And it also has the lowest Pauling electronegativity number.

And with all of this information, we can revisit and answer the question. By considering the Pauling scale, used to qualify electronegativity, which of the following elements is the least electronegative? And the correct answer is answer choice (A), cesium.

## Join Nagwa Classes

Attend live sessions on Nagwa Classes to boost your learning with guidance and advice from an expert teacher!

• Interactive Sessions
• Chat & Messaging
• Realistic Exam Questions