X(g)➜X(g). The type of energy involved in the above transformation is

X(g)➜X-(g). The type of energy involved in the above transformation is

A. ionization energy

B. sublimation energy

C. lattice energy

D. electron affinity

The correct answer is D. electron affinity

Explanation 

The transformation shown in the equation is 

$\text{X}\left(g\right)\to {\text{X}}^{-}\left(g\right)$

. This process describes a neutral gaseous atom gaining an electron to form a negative ion (anion). The energy change associated with this specific process is defined as electron affinity. 

Why other options are incorrect 

A. Ionization energy is the energy required to remove an electron from a gaseous atom, forming a positive ion (

• 

  $\text{X}\left(g\right)\to {\text{X}}^{+}\left(g\right)+{\text{e}}^{-}$
  ). This is the reverse process of what is described in the question.
• B. Sublimation energy is the energy involved in the phase transition from a solid directly to a gas. It does not involve the gain or loss of electrons.
• C. Lattice energy is the energy released when gaseous ions combine to form an ionic solid, or the energy required to separate an ionic solid into its gaseous ions. It involves a change of state and the formation of a crystal lattice, not a simple electron gain by an isolated gaseous atom. NUMBER ELEVEN