# So i am asked to write the equation representing the third ionization energy for Cr, and what I could come up with is Cr^2+(g)->Cr^3+ + e(not sure if I am right).

For the second part I am told that the electron affinity of K is 48 kJ/mol, and i am supposed to write the equation for which this is the energy change, how would I approach this

b. K >> K+ + e-

## To write the equation representing the third ionization energy for Cr, you are correct in thinking that the equation would involve the formation of Cr^3+ ions. However, the initial Cr is not Cr^2+ but rather Cr^2+. Therefore, the correct equation for the third ionization energy of Cr is:

Cr^2+(g) -> Cr^3+ + e^-

Now, to write the equation for which the electron affinity of K (potassium) is the energy change, you need to remember that electron affinity is the energy change associated with the addition of an electron to a neutral atom in the gas phase.

Since K has a valence configuration of [Ar]4s^1, it readily loses its valence electron to form K^+ ion, rather than accepting another electron. Therefore, the equation representing the electron affinity of K would be:

K(g) + e^- -> K^-(g)

Note that the energy change associated with this process would be given by the given electron affinity of K, which is 48 kJ/mol.

## To write the equation representing the third ionization energy for chromium (Cr), you are on the right track. The ionization energy represents the energy required to remove an electron from an atom or ion in the gaseous state.

For Cr, the electron configuration is [Ar] 3d⁵ 4s¹. When Cr loses one electron to form Cr⁺, it becomes [Ar] 3d⁴ 4s².

The equation representing the third ionization energy for Cr can be written as follows:
Cr²⁺(g) → Cr³⁺(g) + e⁻

This equation represents the removal of an electron from Cr²⁺ to form Cr³⁺, resulting in the release of energy.

Regarding the second part of your question, electron affinity refers to the amount of energy released or absorbed when an electron is added to an atom or ion.

Given that the electron affinity of potassium (K) is 48 kJ/mol, it means that energy is released when adding an electron to a K atom.

To represent this energy change, the equation can be written as follows:
K(g) + e⁻ → K⁻(g)

This equation represents the addition of an electron to a K atom, resulting in the energy being released (since electron affinity is positive in this case).

Remember, it's important to consider the signs of energy changes when writing these equations.