Question

Place the following in order of increasing ie 1. K, Ca, Rb

a. Ca < K < Rb
b. K < Ca < Rb
c. Rb < Ca < K
d. Ca < Rb < K
e. Rb < K < Ca

Answer 1

The correct order of increasing ionization energy for the elements potassium (K), calcium (Ca), and rubidium (Rb) is Rb < K < Ca. This is because ionization energy decreases down a group and increases across a period in the periodic table.

Step-by-step explanation:

The question asks to place the elements potassium (K), calcium (Ca), and rubidium (Rb) in order of increasing first ionization energy (IE). Ionization energy is the energy required to remove an electron from a gaseous atom or ion.

As per the trends in the periodic table, IE decreases down a group because electrons are further from the nucleus and are more easily removed due to less effective nuclear charge. IE increases across a period as electrons added to the same shell are drawn closer to the nucleus because of increasing nuclear charge, making them harder to remove.

Since Ca is to the right of K in the same period, Ca has a slightly higher IE than K. Rb, being below K in the same group, has a lower IE than K. Therefore, the correct order from lowest to highest IE is Rb < K < Ca.

The given options suggest part a), b), c), d), and e) could be considered, but based on the periodic trends, the correct option aligns with Rb having the lowest IE and Ca having the highest IE.