B) How does electron gain enthalpy change along a period and in a group?

Electron gain enthalpy becomes more and more negative from left to right in a period. As we move across a period from left to right the atomic size decreases and the nuclear charge increases

Variation in electron gain enthalpy in the period : in the modern periodic table, on moving from left to right across a period the atomic size of elements decreases and the effective nuclear charge increases.

hope it helps you

Explanation: