Question

Element with highest electron affinity ______

Answer 1

Step 1: Electron affinity

• Electron affinity is the amount of energy released when an electron is added to the neutral atom to form a negatively charged ion.

Step 2: Trend across the period:

• Electron affinity increases on moving from left to right across a period. Because as one moves from left to right in a periodic table, the atomic size decreases, it will attract the electron more strongly, and thus more energy is released.

Step 3: Trend across the group:

• On moving down a group on the periodic table, electron affinity decreases. Because on moving down the periodic table, new valence shells are added increasing the atomic radius. The new orbital is further away from the nucleus, meaning the attraction between the positively charged nucleus and the new electron decreases.
• This concludes that the element from the 17th group and second period will have the most electronegativity and thus most electron affinity. This leads to a misconception that fluorine (F) is the element with the most electron affinity but due to the small size and increased electron density the valance electrons will repel the incoming electron and thus decreases the probability to form a negatively charged ion.

Conclusion: Chlorine due to its large size can accommodate an incoming electron thus Chlorine (Cl) is the element with the most electron affinity.