Question

Considering that both sodium (Na) and cesium (Cs) are both alkali metals, which of the following is a correct description of their relative ionization energy?
A) Cesium has a lower ionization energy because it will form an anion.

B) Cesium has a higher ionization energy because it is smaller.

C) Sodium has a higher ionization energy because it is smaller.

D) Sodium has a lower ionization energy because it will form an anion.

Answer 1

Answer:- C) sodium has a higher ionization energy because it is smaller.

Explanations:- Ionization energy is the energy required to remove electron from valence shell of an atom in it's gaseous form.

More energy is required to remove the electron if the size of the atom is smaller as it's electrons are more strongly attracted by it's nucleus.

In periodic table, atomic size decreases on moving left to right in a period and increases on going top to bottom in a group.

Na and Cs are the elements of same group(first group) and also Cs is below Na. So, as Na is placed above Cs, the size of Na is smaller than Cs and so more energy is required to remove the electron from this smaller atom.

Hence, the right choice is C) sodium has a higher ionization energy because it is smaller.