Question Video: Identifying the Atom with the Greatest Electron Affinity | Nagwa Question Video: Identifying the Atom with the Greatest Electron Affinity | Nagwa

Question Video: Identifying the Atom with the Greatest Electron Affinity Chemistry • Second Year of Secondary School

Join Nagwa Classes

Attend live Chemistry sessions on Nagwa Classes to learn more about this topic from an expert teacher!

Which of the following atoms has the greatest electron affinity? [A] K [B] Na [C] Rb [D] Cs

01:51

Video Transcript

Which of the following atoms has the greatest electron affinity? (A) K, (B) Na, (C) Rb, or (D) Cs.

Electron affinity is the energy released when an electron is added to a neutral atom in the gas state to form a negative ion. It is represented by the symbol 𝐸 ea, and we usually measure it in kilojoules per mole.

Let’s look at how electron affinity relates to enthalpy. If the electron affinity is positive, then energy is released. The enthalpy change is negative, and the overall process is exothermic. Conversely, if the electron affinity is negative, then energy is absorbed. The enthalpy change is positive, and it’s endothermic.

Now that we understand this process, let’s look at trends of electron affinities for the elements given. They’re in group one of the periodic table. Note that we are only looking at first electron affinities, meaning the energy released by the first electron that we add to a neutral atom. The atoms of the elements increase in size as we move down the group because they contain more occupied electron shells. For period one elements, the attraction to an additional electron decreases as the atoms grow larger. If a species is less likely to accept an electron, we say that it has a lower electron affinity. The electron affinity will be less positive.

Therefore, of the atoms given, the one with the greatest electron affinity will be closer to the top of period one. This atom is sodium. Therefore, the atom with the greatest electron affinity is (B), Na.

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

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy