Question

How do you find the ionization energy? I am drawing a blank, and I need to calculate it for beryllium.

Answer 1

ionisation eneregy is the energy required to remove the last electron from it's orbit.

so for a atom if electron is removed from n^th state than ionisation energy is given by (- Energy of electron in n^th state)

for berylium (Be) electronic config. is 1s² 2s² , so last electron is in 2^nd state.

so ionisation energy for berylium is = (-E₂)

this can be caluclated using Bohr's theory. acc. to bohr energy of an electron in n^th state = -13.6 Z² / n² ev

so for berylium Z = 4 and n = 2 so

ionisation energy = - E₂ = -(-13.6 * 4*4 / 2*2)

= 54.4 electron volt

= 54.4 * 1.6 * 10^-19 joule

ionisation energy = 87.4 * 10^-19 joule = 54.4 electron volt