Question

Consider the single atoms of the elements listed. Which single atom would require the largest amount of energy to remove its outermost electron? A) Ar B) Cl C) Mg D) Na

Answer 1

Answer: A) Ar

Explanation: Argon [Ar]  has an atomic no of 18 and the electronic configuration is:

Ar :$1s^22s^22p^63s^23p^6$

Chlorine [Cl] has atomic no of 17 and thus the electronic configuration is :

Cl :$1s^22s^22p^63s^23p^5$

Magnesium [Mg] has atomic no of 12 and thus the electronic configuration is :

Mg :$1s^22s^22p^63s^2$

Sodium has atomic no of 11 and thus the electronic configuration is :

Cl :$1s^22s^22p^63s^1$

As we move across a period the number of electrons are being added to the same shell but the number of protons increases, thus the electrons are being tightly held and thus the atomic radius keeps on decreasing.

Thus the smallest atom would have a tightly bound electron nearer to the nucleus. As argon is the last element of the period, it is the smallest in the period and thus largest amount of energy will be required to remove the outermost electron.

Answer 2

Answer: Option (A) is the correct answer.

Explanation:

The energy necessary to remove an electron from a gaseous atom or ion is known as ionization energy.

This means that smaller is the size of an atom more amount of energy has to be supplied to it in order to remove the valence electron. This is because in small atom or element there will be strong force of attraction between the nucleus and electrons.

So, high amount of energy has to be supplied to remove the valence electrons.

For example, argon (Ar) is the smallest element out of the given options and also being a noble gas it is stable in nature.

Therefore, largest amount of energy has to be supplied to argon to remove its valence electron.

Thus, we can conclude that Ar atom would require the largest amount of energy to remove its outermost electron.