Chemistry Regent Exam August 2022
3. In the ground state, which shell of a potassium atom has an electron with the greatest amount of energy?
(1) first (2) second (3) third (4) fourth
Explanation: If we take a look at the Periodic Table on the Reference Table, potassium (K) is in the fourth row and has electron configuration 2-8-8-1. It has 2 electrons in the first shell, 8 electrons in the second shell, 8 electrons in the third shell and 1 electron in the fourth shell. The higher the shell number, the more energy electrons in that shell have since they are furthest away from the nucleus. Therefore, electron with the greatest amount of energy should be in the fourth shell. Alternatively, since potassium is in the fourth period (row) it should have electron with the greatest energy in the fourth shell.
Answer: 4