CHEMISTRY COMMUNITY

I know that atomic radii increase down a group, but decrease across a period; and ionization energy decrease down a group, but increase across a period.

My question is what is the case for electron affinity? What would be the trend down a group and across a period? And why?

Thanks in advance!

Electron affinity decreases down the groups and increases across the periods because the electrons added are closer to the nucleus creating a stronger attraction and tighter hold.

The electron affinity increases as you move left to right because the rightmost elements have an almost full valence electron shell, making them more desperate to gain another electron to fill the outer shell. Electron affinity decreases moving down because the electrons are in farther shells to the nucleus, decreasing the pull.

As you go down a group, electron affinity decreases as there is more shielding which decreases the electrostatic attraction between the nucleus and electrons, resulting in less energy released when e- is added to a gas phase atom. However, as you move across the period, electron affinity increases as electrons are added to the same energy level and the atomic radius decreases, increasing the attraction/electron pull.

Electron affinity decreases down a group of elements because each atom is larger than the atom above it, and also increases left to right across a period. With a larger distance between the negatively-charged electron and the positively-charged nucleus, the force of attraction is relatively weaker, causing the electron affinity to decrease. Moving from left to right across a period, atoms become smaller as the forces of attraction become stronger. This causes the electron to move closer to the nucleus, which increases the electron affinity from left to right across a period.

When thinking about electron affinity think about how close the electrons are to the nucleus (where the protons are). Electron affinity increases the closer the electrons are to the nucleus, so it increases as it goes up and to the right