Question

As we move down a group in the modern periodic table, the electron affinity of individual elements -

• A. increases
• B. decreases
• C. remains same
• D. increases and then decreases

Answer 1

The correct option is B decreases

Electron affinity is the ability of an atom to accept an electron. The more negative the electron affinity value, the higher an atom's affinity for electrons. Electron affinity generally decreases down a group of elements because each atom is larger than the atom above it. This means that an added electron is further away from the atom's nucleus compared with its position in the smaller atom. With a larger distance between the negatively-charged electron and the positively-charged nucleus, the force of attraction is relatively weaker. Therefore, electron affinity decreases. 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, thus increasing the electron affinity from left to right across a period.