Question

Which of the three has the largest ei1? which of the three has the largest ? 1s22s22p63s23p64s1 1s22s22p63s23p5 1s22s22p63s23p1?

Answer 1

$E_i1$ will be largest for $1s^22s^22p^63s^23p^5$.

Explanation: Ionization energy is the energy to knock off an electron from a gaseous atom of ion. First ionization energy or $E_i1$ is the energy required to remove 1 loosely held electron from 1 mole of gaseous atoms to produce 1 mole of gaseous ion carrying (+)1 charge.

$M(g)\rightarrow M^+(g)+e^-$

The electrons are filled according to Aufbau's rule and the orbitals which are strongly held to the nucleus follows the order $s>p>d>f$.

Electron is released from the outermost shell that is from the electrons which are loosely held to the nucleus, this follows the pattern $s$.

In configurations, $1s^22s^22p^63s^23p^64s^1,1s^22s^22p^63s^23p^5\text{ and } 1s^22s^22p^63s^23p^1$

The loosely held orbital is 4s, therefore electron will be lost from that easily.

Now, in 3p orbital, one configuration has 5 electrons and one has 1 electron.

The configuration having 5 electrons will be more tightly held by the nucleus because it has more electrons that the one having only 1 electron. Hence, the electron will be lost easily from the configuration having $3p^1$ as the valence shell.

Therefore, the configuration $1s^22s^22p^63s^23p^5$ will the largest $E_i1$.