Question

which of the following elements has the electron configuration shown below for a neutral atom of that element?
$1s^2 2s^2 2p^6 3s^2 3p^6 4s^1$
a calcium
b potassium
c argon

Explanation:

To determine the element, we calculate the total number of electrons from the electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^1\). Summing the exponents: \(2 + 2 + 6 + 2 + 6 + 1 = 19\). A neutral atom has electrons equal to protons (atomic number). Calcium has atomic number 20, argon 18, and potassium 19. So potassium matches.

Answer:

B. potassium